Pelvic pressure with twins

I'll be 22 weeks with my twins Wednesday and Im wondering is it normal to have pelvic pressure when sitting or laying too long. I usually have a lot of pelvic pressure and back pain in the mornings when I wake up and its hard to walk. The discomfort usually goes away within a couple minutes if I move around. Does anyone else experience back pain and pelvic pressure particularly in the morning when you wake up or even when sitting too long?