So, is there a way to adjust keyboard sensitivity in Sonar x2? For some reason, in sonar my keyboard velocity sensitivity just drops and I really have to mash the keys when recording, I'm hurting my fingers and I think I will eventually break my keyboard this way.

This is usually a setting on your physical keyboard.
 
What sort of velocities do you get in Sonar when playing normally?

Well, when playing at medium dynamics I usually get something around 50 and in other software its about 70-80. I have a studiologic tmk88 keyboard, and there are no sensitivity adjustments on the keyboard itself.
 

Velocity data are embedded in the MIDI Note On messages sent from the keyboard. SONAR can alter them on playback by various means, but the velocities recorded and shown in the Event View will be whatever the keyboard is sending. The only other possibility would be that your interface is altering them on the way in.
 
 

A quote from homerecording.com thread:
 
"I've a TMK-88 and it's fine for organs, strings etc but I want to throw it out the window for piano... it has a naturally low velocity curve and notes jump out and in unexpectedly all over the place."
 
Other contributors have reported variable velocity output from different keys. Sounds like not great piece of kit. Possibly yours is sending lower velocities as it ages...?
 
You can have SONAR compensate by raising the Gain (formerly Velocity Offset) in the MIDI/Simple Instrument track. This offset affects both echoing of live input, and playback of recorded MIDI.
 
 
 

 
MIDI Solutions Velocity Converter.  Check out the curves in the manual (or programmable user curve or velocity via CC message).  A most appropriate name for this company.  Every MIDI hardware enthusiast can solve at least one longstanding problem in this product line.
 
I have no stock in this company, but I know good products when I see them (I own several).  It's Anatek reincarnated.

Try resetting the keyboard. I have a Studiologic SL-880 and sometimes I need to reset it. (Hold down Up, Down and Enter buttons and power on).