I've had that. It felt bruised. I assume it was from the hips/pelican bone spreading. I got a massage, and she got into the gluten and I wanted to die! This all started around 12 weeks or so for me and still flares up now at 16 weeks.
I had sciatic issues as well. Lower back, right through butt down the leg. Pillow between legs and Moms old saying of get up and move around, you'll feel better...actually worked. I just needed to keep good circulation through that area. If it is from hips widening, it will go away soon.
Re: Physical pain