First of all, if possible, you should see a doctor - that's where you'll get your best advice, since he'll actually be able to check your shoulders. However, sometimes you don't have health insurance or there is some other impediment to seeking medical advice, so I'll throw in my penny (don't think it's even worth 2 cents).
Shoulder problems are common with heavy lifting, especially when using AAS. Steroids inhibit the development and growth of tendons (someone else put some great articles regarding this in the anabolic forum - i'm just too lazy to find them right now) and they cause rapid development and growth of the surrounding muscle. So basically, your pushing weight that your muscles can handle but your connective tissue can't since it needs more time to catch up. These problems can be exacerbated by things such as incorrect form on the bench.
I'm not about to offer any type of diagnosis, but I have shoulder pain as well. I've eliminated incline press and shoulder press from my routine since they were just too painful. I go light on the bench and go really heavy on the decline since that doesn't hurt my shoulder at all. Ice has also become a good friend of mine.
Good luck.
