ok i did try messing around with the bass/treble/loudness

when i put the bass up the music distorts at a lower volume then when it was at 0. I am not running an amp, unless the deck has a built in amp that iam not aware of

 

Yes the deck has an amp, a tiny little one that struggles to produce clean power when the volume level is turned up. The speakers are distorting because of how you used the system. What you need to do is play the front speakers only and find out where the redline is, after that go no higher with all speakers playing. Want it louder, add bass blockers to the front 4" speakers and you can re-evaluate the redline. Want it louder yet again, buy an outboard amplifier.

 

would it make a difference if i added two 4'' speakers to the back? since i only have 2 in the car now?

 

No, you will more than likely exceed their abilities as well. What you are doing is expecting too much from something too small. Find some bass blockers for the smaller front speakers, continue to use the 6x9's in the rear. Learn how to use your stereo and this may not happen again.