[UConnJulie]

Well, a lot going on with you ... you say you saw your GP, but did you see an orthopedist as well? Honestly, it sounds like you had a lot more than just "soft tissue injury". Soft tissue heals relatively fast, but a chronic AC joint issue does not. For sure you have some instability issues from the repeated trauma.
If I were you ...
1. Go see an orthopedist. Preferably one who deals with shoulders as a specialty. He/she should have a greater appreciation of what you need to get you back to your sport in the shortest amount of time.
2. Focus on rehab/mobility/stabilization exercises for now. Have someone knowledgable look at your scapular stabilization patterns (ie with movement) to see if your lower trap is firing when it should and make sure your upper trap isn't firing when it shouldn't. Also have them look at your static scapular positioning (pain can alter the natural position of the shoulderblade, and if you are holding it in an abnormal starting position, it can alter the entire mechanics of your shoulder movement).
3. Find a good physical therapist who understands the rigors of your sport, and can help you (with exercise, and good manual therapy when indicated) get back to it.