Mics like the SM7b will pick up less of the "room" (less noise as well)...
Still sounds like the OP needs to find ways to reduce the noise (ie: quieter computer fans/etc)... then use gobos/reflection-filter/etc to minimize noise captured by the mic.
 
The OP could start by recording the noise-floor (as it is now).
Then, apply various techniques discussed here/elsewhere... and re-record the noise-floor.
That would allow direct comparison... and the OP would learn what's effective.

Ok ...good pointers....let me try some of them. 

RishiS
I know it's subjective but how high is the mic  gain set usually for recording.I dial in around 40 to 45db on the gain knob in totalmix to be able to hear my voice (while the mic fader is set  almost to the top)

How much gain do you need? As much as it takes to get a solid level without clipping into your DAW and not a dB less. How much gain you need depends entirely on the mic you're using and the sound pressure level of the source you're recording.

If you're getting a good level into the DAW but its got too much room noise on the track, you've either got to quiet the room down or move the mic to a quieter room and record from there. When I rebuilt my DAW computer, I spec'd everything in it for low noise. The power supply is fanless. The OS and plugin library drives are solid state. The audio drive is a traditional spinning hard drive, but db level was one of the considerations when I bought it. The CPU choice was compromise between raw horsepower and typical operating temperature which allowed me to use a fan that's all but silent most of the time.
 
Right now the hum from the display on my old A80 is the loudest thing in the studio. I just shut it off when I'm using live mics in the room. 

I'm satisfied with the recording levels but the issue really is not  being able to hear my voice in the headphone while recording unless I push the gain high n that causes all the noise to get amplified as well. I guess I have to find ways to isolate the mic.

Apologies but I'm not quite following. What do you mean exactly when you say you're satisfied with the recording levels? Does that mean they're where they should be i.e. the loudest parts stopping just short of 0db? Or does that mean they're loud enough to give adequate signal level on the track for anything you'll need to do with it during mixing but not necessarily as loud as it could be in the track?
 
I'm confused because in theory anyway, if the level were where it should be and you then added more gain, you should probably then end up with some signal clipping. Since this doesn't seem to be the case, I would suggest that your signal level probably wasn't where it should have been to begin with.

This further leads me to speculate that if your recorded material was sitting fine in the track at that lower level with no noticeable room noise, I would go ahead and set the gain at the higher level where it really should be. Then just pull the track level back during mixing and most of your room noise should fall back below the noise floor where it was when when you were recording with less gain. If any little bits are still creeping through, you should in most cases be able to control that with a noise gate during mix down*.
 
Of course if you're trying to record something like an acoustic guitar or a ukulele or even a voice that will be out front with no other instruments behind it during part of the track, you may find the only way to really get that down is to find a quiet room somewhere else in the house, get some long cables and run your mics and headphones there. Having someone else engineer for you is pretty much a requirement in that case but the results are usually worth it.
 
 
 
 
 
*I'm not a fan of using gates during tracking. Its way too easy to think you've got good stuff down during the session only to realize later during mixing that your gates were closing too quickly and you've lost important parts of the performance which you can now never get back.

RishiS
I'm satisfied with the recording levels but the issue really is not  being able to hear my voice in the headphone while recording unless I push the gain high n that causes all the noise to get amplified as well. I guess I have to find ways to isolate the mic.

You can set up the interface in Totalmix to give a high output to the headphones with a lower level going to the DAW.

Set the input gain to where it needs to be to get the tracking level correct. Then click on the label at the bottom of the channel strip and select a headphones output. You can then use both the headphones output fader and the input track's fader to set the headphone level without affecting the level being sent to Sonar.

You need Totalmix s operating mode set to "free" to do this, in that mode Totalmix is a huge mixer with the ability to route different levels of anything anywhere at the same time.

https://youtu.be/NVa3AyUNGuI
 
I made a video looking at how to use TotalMix looking at only a single Mic input.

From my experiences with a Fireface 800 anyway the headphone output on the front of the RME interface are linked to outputs 9/10 from memory. The headphone output does not normally work under normal conditions.  I had to create a buss in my software and route it to outputs 9/10 and then send whatever I wanted to hear to that buss.  I think this might be the issue.
 
OK I have just checked and the headphones on the UCX are routed to channels 7/8. So basically you won't hear anything in your phones until you send something to outputs 7/8.
 
The OP may not have read his manual properly. But this is a weird RME thing and I have encountered this before. The phones should probably default to outputs 1/2 instead but they don't for some reason. It certainly fooled for me for a while too!
 
I am thinking this may be the problem.  While Geoff's video is interesting and useful I don't think it is dealing with this basic issue. The OP is not hearing anything in his phones. Or least I am hoping so.  Once you get this sorted the headphones will blast you with output level.

The issue really is low levels of my own voice in the headphones when I'm trying to record. Raising the gain n fader levels on the mic input in totalmix makes a lot of environment sound like cpu fan audible.
I tried the expander technique mentioned by gswitz...it does solve the noise issue.Im curious to try what tlw mentioned about free mode in total mix.
Thanks to all for the great tips !

This can be easily fixed in TotalMix.  You can send any signal anywhere. And you can save these mixes as Snapshots.  I have a Snapshot saved that routes all channels to headphones - it's one click away when I need it. No need to even open the mixer. I found these very helpful and better than reading the manual (the visual of watching somebody perform the action makes it so much easier to remember for me):
 
RME Total Mix Tutorials (YouTube)