Sorry to hear about your hip probs Elliebeth, so spoke to my boss who's a Biomechanist ( only 18 in the UK) and he has GPs, Physios, Pilates and Yoga teachers, Osteopaths and Chiropractors as clients.
He says you could well have something called 'Olechranon Bursitis' which he's dealt with quite a few times in his 47 years of work. On the outside of your hips, you have fluid filled sacks called bursae, which act as shock absorbers and if these get inflammed you can get the reactions you describe.
You need to put that into the frame and voice the possibility to your GP. My boss says it's very unlikely indeed to be sacro-iliac related, but as he can't examine your personal Biomechanics and what messages your movements are flagging up, he wouldn't attempt to advise further.
He did say that unfortunately for quite a few people who's bodies don't actually suit Pilates or Yoga ( both these have numerous flaws as well as good things) doing them can actually escalate problems, a statement which surprises many people, but is nevertheless a clinical fact. x