Best Solutions for Back Pain

21w with twins. I have a lot of back pain already because they hang lower, but these munchkins are only 12oz each. They’re supposed to be 5lbs each by the time I deliver. I used to have lower back pain and it’s been moving up into my mid back. Any recommendations on pain relief? Better stretching, pregnancy belt, something else? I’m only halfway through and it feels like there’s not enough available that can make this better right now.