Is ok to lay on my belly if im 12weeks pregnant?

Sure. As long as it is comfortable for you. As you progress in your pregnancy, it's a good idea to begin laying on your side or back. During your 2nd or 3rd trimester, laying on your stomach can decrease blood flow (via the placenta) to the baby.
Sure. Sure, as long as it's comfortable for you. As you progress in your pregnancy, it will be important to start lying on your side or back, because lying on your stomach in the 2nd or 3rd trimester can decrease blood flow (via the placenta) to the baby. They also sell pregnancy pillows to help conform to the body.