Hi Danni,
It is ok to sleep on your tummy as long as you are comfortable. I love to side/tummy sleep, but have already got a bump that feels like a ball under my tummy if i roll to much onto my tummy, so cant sleep on my tummy anymore. It is uite painful as well if i roll onto my tummy, so i have to get up and flip over to the other side instead. you wont hurt your bubs in any way hun, so enjoy it as long as you can