Sleep position paranoia

I'm 32 weeks. Since the third trimester I've been making an effort to sleep on my side as advised. Whilst I fall asleep on my side with no issues very soon when I wake up I realise I'm on my back. They say you spend most time in the position you fall asleep in but typically not the case with me as sometimes I wake up soon after and I'm on my back! My midwife said that as long as I use a pillow and I'm not totally flat on the back it's fine. I'm worried I'm restricting blood flow to baby. Contrary to what I read online it's not uncomfortable at all for me to lie on my back. Wish it was! Tried pregnancy pillows but I don't find them as comfy as sleeping without one. Maybe I should try to persevere with that? What's your views on sleeping position?