Shoulder instability

For the past couple of months, my shoulder has been feeling "loose" or instable. I have some moderate pain and mostly the very odd feeling that it just is about to fall out of its socket. It usually feels okay while swimming but very bad afterwards. I've taken the past week off from swimming in the hopes that things would feel better, but no dice. I do have a call in to my doctor, but I've done some Googling around and it seems like it might be multi-directional instability of the shoulder. Does anyone have any experience with this? I am physically unable to participate in most other cardio (running, step aerobics, anything with any level of impact) so the idea of not being able to swim is very depressing.