pai in my elbow

Hello- I am 17 and a high school pitcher. Over the winter I’ve been going to an indoor baseball complex and throwing about once a week for 3 months. Now, I’ve started pitcher’s practice and my elbow always hurts after practice. I try to warm up, but my coach doesn’t give us a lot of time to. In practice, we use med balls and cords at the beggining of practice after that we throw long toss and then we throw 30 oz. balls…all of this is to be done at full speed as hard as we can throw them…is this good? why does my elbow hurt?
It never did in the winter.