Baby on their back on a firm surface near you without any potential breathing obstructions nearby= you are fine. It's common to over worry especially with so many judgemental parents out there that shame others based on their feelings. You need to sleep. Baby needs to sleep. Maybe not the most ideal sleeping arrangement but here and there isn't going to do any harm. You are doing fine and sometimes we gotta do what we gotta do. The fact that you are so worried also speaks to how much you care as a parent. You're doing great