Whats wrong with my shoulder

I hurt my shoulder doing weights, although i cant put it down to one specific occasion. It is a pinching pain where my pec joins the shoulder, just under the collar bone. It has been sore now for 2 months. In the early stages it was sore to touch but i could massage it better. Now it is not sore to touch and not sore when moving my arm in any natural position.

However it is sore when i attempt to lift weights, especially the bench press or dumbbell curl. I was benching 100kg before injury and now struggle with 60-70kg.

Have tried resting it for 2 months but am getting really fed up. Im back at the gym doing really light weights to see if that helps.

Does anybody know what this is and what i should do. It is getting better but unbelievably slowly.

Cheers