Not until baby gets bigger. I've had the same issue because I'm a stomach sleeper. I've asked my doctor if it would hurt the baby and their response was no. Usually, once you get into your second trimester is when you really want to avoid it. But if you don't feel comfortable sleeping on your stomach, you can always try putting a pillow in front of you when you sleep and try holding on to it throughout the night. Right now, if you wake up on your stomach, it's not going to affect baby. EVENTUALLY your belly will be too big to roll over. Lol. Hope this helps...
your only 6 weeks :) you CAN lay on your belly :) worry about the baby when there is a bump, then don't lay much on your belly :)