Back pain even with a preg pillow

Hello! I am in need of a bit of advice. This is my first pregnancy, I am 28 weeks and am finding that I have back pain when I sleep. I have a U shaped preg pillow that goes along my back and front, I use it every night. I always sleep on my side with my knees bent and pillow in between. I also tuck the pillow under my belly because I found that helps, tuck the back side under my back a bit, but still have lower back pain. Am I just to the point that I will have that because our girl is getting big or is there a way to help with this?