I checked out youtube and looked at a few videos that tennis coach's have posted and started messing around with my forehand stroke. I eventually found that my problem was mostly because of my keeping my wrist tight during the stroke. When I relax my wrist, I don't feel the pain. I was also constricting my shoulder movement, so freeing that up helps loosen things too.
It also appears that relaxing my wrist during the forehand shot also increases the racket speed by a lot (since when my wrist was tightened it was straining against the forward movement, and now it contributes to it).
Hopefully this knowledge might help someone with the same problem, if anyone else is stupid enough to get themselves hurt like this