Back pain... hallpppp

Today my back has been pretty painful and I'm just uncomfortable. I went to a baseball game with boyfriend last night and the seats were really uncomfortable and we had to walk like 7 minutes each way to get to/from the car and I was not wearing supportive shoes whatsoever. I'm 17 weeks and can feel my posture changing to accommodate my growing belly and weight gain. I think that's why my back hurts today, because of last night. We have a brand new really nice bed so it's not that... I'm laying down in different ways on my side, with pillow between legs, on my back with pillow under lumbar area... any tips for relief?? My whole back is uncomfortable:(