i was told my chest is heavier then my back thats y i cave in with my shoulders or what ever =/, how do i fix this and how long will it take? how often should i do the back exercises?

You should train proportional, do not disregard any muscle group.
Now you should train the smaller muscle group more harder, about 2 times a week but don;t forget about the rest.

i assume you mean your chest is over-powering your upper back, this would result in your shoulders slumping forward, the best way to correct this is to perform more posterior work....great exercises for this are the rear delt laterals/reverse peck-deck/rear cable cross-overs.....anything like that, even rows to a certain extent....i had same issue when i started training...- too much chest and arms...lol slouching and poor posture can also cause probs....

thanx yama exactly what i needed =]

you could try push ups with your finger tips touching directly under your chest or form a triangle with thumb and fore fingers. Another good thing to do is stretch the back by doing bridges, like the wrestlers do. Along with those yam mentioned. Maybe olympic stlye lifts would be a good idea if you can do them.
I hear that this problem you have can result in the ripping or shearing of the bicep muscles if it gets real bad from the shoulder.
Good Luck!

You should work more on your rear part. Now you learn your lesson, don't focus on only one part, work even and don't forget the rest.