Tensing/cramping on winny??

Anyone else get this?

It's like when I reach around with my right hand over to the back of my left shoulder my entire right shoulder tenses up almost like a cramp. I almost knocked a plastic cup off the counter but quickly grabbed it out of a quick reaction. My right pec tensed up to the point of hurting like hell.

I've had it before but never to this degree. It's happening in my quads as well. I'm starting to get really strong and put on some size (EQ/winny cycle) and I'm afraid I'm going to pull a muscle.

I'm taking all kinds of supplements including a chondroitin/glucosamine /MSM stack for the joints. Getting plenty of potassium as well (I think).

Any ideas? Thanks.