After playing several days in a row this weekend, I'm experiencing some pain in my right shoulder. I'm worried it's coming from my flawed serve motion, namely the level shoulder angle in my trophy position. I understand it's a rather unhealthy position for the shoulder, but I just can't seem to fix it. Since I've been having some pretty decent results with my serve, I haven't bothered much. Could this be what causes the pain or could it be something else? I'd say my technique in my groundstrokes doesn't have huge flaws, so I don't think that's where the problem lies. Or is it just overplaying, having played for 5 hours in 3 days?