Welcome to third tri! I feel your pain unfortunately. I have also been diagnosed with PGP and my Dr told me that yoga is one of the best things for PGP. I have kept up my classes and spoken to the teacher about specific exercises to help me. If anything doesn't feel right, like yesterday it was squats, then I don't do it and she tells me something to do instead such as scoops.
If you're in the UK it's worth speaking to your midwife as you can sometimes get maternity bands from them for free. Also I have borrowed a birthing ball from my friend as it can help to sit on one instead of slouching on the sofa.
The main thing is when getting up or sitting or turning over in bed keep your knees together, helps a lot. Also try not to lift anything even remotely heavy and try to avoid going up and down stairs too often.
The doctors and midwives I have spoken to have said it actually helps a bit in labour as the ligaments are all relaxed and it's a bit easier to push baby out. I'm hoping for a home birth and have been told that there is no problem with having a home birth with PGP and it may even be the best place for me so they obviously aren't worried about it affecting the birth.
Sorry that was long, I've been doing a lot of reading up on it recently!