7 weeks is pretty early to have to give up sleeping on your tummy. I would suggest sleeping on your tummy with one leg bent upwards towards your chin to relieve some pressure. Then the next stage would be to put a small pillow under that knee to raise your hip up further. You'll know when you cannot sleep on your tummy anymore, you will literally feel that your uterus is no longer tucked into your pelvic bone. I'm 11 weeks with twins and second pregnancy and still able to sleep on my tummy. I do notice, however, that I am basically an insomniac after about 2-3am and am keenly aware of any sort of goings on in my belly area while I sleep which I less notice when sleeping on my back or side. Too bad I get headaches from sleeping on my back. I don't look forward to losing the ability to sleep on my belly. Especially if I have to have another c-section.