I'll prefex this first by saying it needs to be assessed by a physician.

Based on your discription "over time" and without exam and past history information, I would suggest it is a chronic tear which develops over a period of time more so than an a acute tear which tends to happen as a result of a sudden, powerful movement. Cronic tears usually occur at or near the tendon, as a result of the tendon rubbing against the overlying bone.

Ladyfisher advise is as good as your going to get in the next 5-8 days and add a sling, unless you are open to having a steriod injection which will enhance healing period.

best of luck