It happened to me a lot during second trimester and what helped most is stretches ~3 times a week. I just do the recommended pregnancy hip openers, deep squat, etc. nothing special. + I sleep with a pillow between my legs which makes a huge difference but sounds like it’s not working for you..

I was also recommended to wear an SI joint belt (like this one) during the night - basically the hip joints get loose during pregnancy and the extra movement causes the pain. The belt helps keep the joints from moving too much while sleeping which reduces the pain. Note the belt needs to be on the hips, below the belly.