Actually you don't want to leave this unattended because it will quite probably get worse. I'd do some adjustments on your budget and make the trip to the physio. Whatever the problem is, they will figure it out. if it's pelvic, hip, nerve, sciatica ... it's all related.

My pain started around week 29 and I saw a physio. She did some adjustments and it helped so much from just 1 visit, but I wasn't diligent about doing all those things Raven listed so the pain returned and I let it go without attention and now it is 10 times worse. I called my physio today and snuck an appointment in for thursday, and that's not soon enough.

My Ob was supportive. He warned me it would get worse and to call the physio but I didn't want to pay to see the physio again. Now I'm at a point where I don't care, I'll dig the money up from the depths of somewhere just to be able to stand, sit, sleep, walk etc again.

This particular pain does not fix itself.