Hi, I registered to this site so I could log in and see if my suggestion helps you. I am familiar with this pain, most particularly when pregnant with each of my two boys. I feel like you may be experiencing some sciatic nerve pain, and luckily the solution is pretty simple. Stand facing a chair or something to hold on to, bend at the hips so that your body forms a 90 degree angle, then have someone push your hips together. It won’t take much pressure and you will notice a difference immediately. It also helps for days, even weeks, at a time.
Please give this a try and post your findings.