Just another quick thought about the Melodyne fix. It really isn't that hard (and likely much easier than using a pitch wheel). ll you have to do is...
 
a) Import the audio file
b) Select the clip and enable Region FX > Melodyne (if you have X3... otherwise you could use V-Vocal but that would be different)
c) Just select all the blobs (Ctrl A...) and nudge them up or down until the first note of the clip matches a tuned note on the scale.
 
If you sung the melody in tune with the first note your work is done... otherwise you could use the detect features to automagically make all the notes snap into place using a chromatic scale or an appropriate diatonic scale/mode or if it is a short passage or only a few notes are out of tune you could just select the out of tune blobs and fix them.
 
Clone the track (actually you should clone the track before doing the pitch correct so the original is intact) and bounce the corrected version so you have your hummed track in perfect pitch. Then if you want a MIDI version to use as a starter you can just create a new MIDI track, select and drag the corrected audio track and kablammo... your melody will now be in the PRV ready to use.
 
If there is minimal note by note correction this whole process could be done in a couple minutes.
 
This is all theoretical on my part though because I haven't actually tried Melodyne yet (because I'm busy with other stuff... but really should because it looks cool) and am only basing that on the tuts I have read/watched but it really should be extremely simple.
 
So yeah... starting your recordings at a proper pitch from now on will help but for stuff you already have recorded that's how you can easily fix them up. I recommend watching for Karl Rose's SWA X2/X3 vids to go on sale because he is very thorough in describing this and most other aspects of Sonar X2/3. I picked it, and the Rapture tut, for $20 on sale after doing the Cakewalk survey (so I actually got them both for free with the coupon).
 
The Cake TV section has some Melodyne vids too that might describe the same procedure.
 
Anyway... that's just how I would go about things. I'm a little weird and crazy though.
 
Cheers.

Thank you for your good explanation Beeoster. I think I have not made it clear the way I do the humming to computer job. First I hum and then later I listen the hummed stuff and play it on my midi keyboard. It helps me when I use the pitch wheel because I can easier listen and translate on the keyboard the melodies I hummed when the notes are at the right pitch or on key. I don't know why it is that way. I am not sure if this made things quite clear because I don't know how to explain it in english.

Yeah, I prefer to do things manually too whenever possible.
 
Here is another suggestion...
 
Instead of using the pitch wheel you could use the controls on the MIDI track or in the virtual synth to fine tune the outpout of the synth to the recording of you humming. So pick the note on your keyboard you want to start the melody with then play that note and adjust the fine tuning of the MIDI track/virtual instrument until it matches the first note of the recording. Then you can figure out the part without the pitch wheel, lay down a MIDI track then just tune it back up to a normal pitch.
 
Just a thought.
 
Oh and I think if you turn the clip of you humming into a Groove Clip (select the clip > right click > Groove Clip) open the Inspector (press I) and there is an option to increase/decrease the pitch of the audio clip. It's been a while since I looked at that feature though so I may have gotten that wrong.
 
Either way... lots of ways to do this. Cheers.

Thanks again Bleepster for the excellent tips. I think my real problem is composing good melodies and that is a big one.

Thanks to Bleepster, I have finally gotten a midi keyboard phone app. I have already done some simple melodies with it. It is handy to be able to use a keyboard anywhere and it cost nothing. I am a bit shy though and I fear people who find me humming or phone midi playing, in a store for example, may think I am a bit cuckoo:D

kakku
Thanks to Bleepster, I have finally gotten a midi keyboard phone app. I have already done some simple melodies with it. It is handy to be able to use a keyboard anywhere and it cost nothing.

Hehe...  "Bleepster!" 

Oops. No harm intended. It is just my crappy memory modules that sometimes miss a couple of bytes. So, thanks to Beepster!:)

Heheh... no worries. "Beepster" is just another in a long line variants on my actual nickname and the "Bleep..." extension has been in that mix as well.
 
Glad I was able to provide a useful suggestion. As far as weirding others out in public that's part of the fun of being an artist. However if your phone has a mini jack or a way to connect an earpiece that would be a good way to work in silence. It would just look like you were browsing the net or texting while listening to tunes.
 
As far as the humming... that is far less weird and obnoxious than some of the crap people do in public in the "American Idol" generation. At least you are busting out weak gangsta rap rhymes or trying to squeal like Mariah Carey or some sh*t. Now THAT is obnoxious. lulz...

I want to use my cell phone as a bluetooth mini-touch midi keyboard...then i could really rockout! -S

That would be cool. Update: I do not need to use pitch wheel for translating my hummings any longer. Although I hum in a way that most sane people would call sheer ear drum torture, I still do it and with some success...