Lie flat on back while sleeping

From what I remember, lying flat on your back from the second trimester onwards is something most gynae and midwives advise against, because the weight of the uterus can press on a major blood vessel and reduce blood flow to you and the baby. That said, some mums find sleeping on their side with a pregnancy pillow between the knees actually helps with shoulder tension too, so it might be worth trying that as an alternative. The main thing is you want to feel comfortable but also keep circulation going well for both of you. I'd really recommend bringing this up at your next gynae visit so they can advise you based on how your pregnancy is going specifically.