Congratulations on your exciting news! Stomach sleeping should be fine during pregnancy. Your baby is surrounded by a sac of fluid which prevents any damage while you're in this position. And lying on your belly allows for appropriate blood flow and circulation (as opposed to lying on your back, which can compromise circulation in the second half of pregnancy.)
As your belly grows, however, it will become more difficult to lie flat on your stomach. You will probably find it more comfortable to lean slightly toward the side in order to take direct pressure off of your belly. You can purchase a body pillow to help you comfortably lie in bed with support for your belly. I have also heard of foam cushions for pregnancy with the stomach area cut out, designed to allow women to lie directly on their belly without experiencing excessive pressure in this area. A cheaper alternative would be to buy an inflatable child's swimming ring; try placing your belly in the center when you go to sleep.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.