btw, if you suspect you have rotator cuff problems, maybe add some specific exercises at the end of a workout 3 times a week and try to stay away from exercises that irritate it - so basically every chest exercise. This is what I had to do, took about 2 months then another 6 weeks of slowly working my way back into it.
I'm now about where I left off before my shoulder started hurting, and its feeling great (touch wood).
Yea your chest will lose some size, but it comes back quickly. My friend had a similiar problem but couldn't face the fact he would lose muscle so he kept training and now his shoulder is 10x worse.