Never not injured from running

Hi! This forum recently, but haven't been able to go to any of the group yacht runs yet because I am of course slightly injured. I get a different injury just about once every six months and it could last up to three months. For context, I became  mtriathlete year just because I wanna keep working out but I kept getting injured from just doing running alone. I was doing 50mi a week for a while and felt strong, but got injured from that so started swimming and biking.  I really do love just running, so is  there any recommendations on how to combat this so I can run everyday again? 

Basically, at this point, the only injury I haven't had is shin splits, but I suffer from lose back, knee, and especially hip and pelvic pain. I get MRIs and see a physical therapist and usually it's just bursitis or some type of overuse, but I know runners that run more than me and don't get these issues