I tried to teach myself to shoot lefty, but found that it confused me at crunch time, when I tend to go on autopilot and try to revert to many years of doing it "right". I don't think that's a good solution anyhow, because you undoubtedly shot too heavy and/or too much, which created the problem. You have to change your habits, unfortunately.
I have had no shoulder problems at all this year, but it took several months of rest to get here. It's hard, but for me it's necessary. I just can't shoot as much now as I did in the past, the result of overdoing it with a heavy bow. I almost never shoot groups at a target anymore, because that aggravates the problem. For practice, I shoot one judo arrow while roving, and it keeps me from hurting myself. I'm fortunate to live in the country, with plenty of room for roving, but you can get by if you have a yard big enough. Sometimes I just circle my house, one shot at a time.
There's a benefit, too. Roving and taking single shots at random distances is the best hunting practice you can get!