I just play recreationally and have no formal training. Last weekend I played for around 2.5 hours with a lot of fast serves. After two days, my bicep area on right hand became sore and hurt badly when pressed. I can still play but can't lift my hand over my head to serve. Also when I carried a heavy bag, I noticed small pop in the right shoulder. Left arm also hurts little bit. What am I doing wrong? Bad serve position? Bad leg position? The racquet is Babolat drive z os with 4 3/4 grip @ 55lbs. The racquet feels good and easy to hit with. The pain is greatly reduced now but I can still feel it little bit. Thank you for any information.