Shoulder discomfort on bench

Hello T-Nation,
I figured if anyone could help me it would be the Nation! I have been doing a heavy bench pressing program which is coming to an end this week. My question is this. Over the last week after doing heavy bench press and/ or heavy dumbell press (for me anyway) I have noticed some discomfort (tightness in my right trap. Then about an hour later it feels tired and at time I’m experiencing spasms in it. Is this the beginning of something far worse? Is there something in my form that is causing this trap to work harder than it should? Any help would be appreciated.
Gumby