So I guess I'll explain my story first. Right now, I am about to turn 17 and I am a 4.0 player who is very close to a 4.5, but my serve is just destroying my game. At the beginning of the last summer before this one, I was finally getting my kick serve settled. I was very happy, and I continued to serve baskets and baskets. Unfortunately I was getting a pain in my arm that day and I later on found out I had tennis elbow. For the next half a year I would actually not serve a single ball due to too much pain, but I did continue to play despite that. During this time I made some changes to my game to recover my arm such as using a less extreme western forehand (It was almost at a hawaiian and I think this is what caused it in the first place), and a less extreme grip on my one handed backhand. After this time I started to serve again because my tennis elbow was finally better. However I believe I lost quite a bit of flexibility with my shoulder and back. My serves lost a lot of pop, especially my first serve, and I just completely lost my consistency despite how many baskets I serve. Now to even top that off, I have gained two pains in my shoulder over the last month that don't seem to go away. One is right below my neck on the right, and the other pain (The bigger one) is under my shoulder blade. It hurts really bad when I try to serve really hard (Especially when I hit a big kick serve and I contort my back) or if I try to throw a ball really far (Makes sense, it is the same motion as my serve). My coaches have already told me that I don't do anything too funky on my serve. So my question is, could back flexibility play a role in why I am getting these pains and why I can't seem to develop my serve back to my serve of old?