Still sleeping on your stomach?

C
How many weeks were you when you stopped sleeping on your stomach? 
I'll be 14 weeks tomorrow and this past week I haven't been sleeping on my stomach very long. Maybe a hour and then I have to switch to my back or side. This is not normal for me as I've always been a stomach sleeper. Idk if it's a mind thing and I know my baby is there or if I'm truly uncomfortable? Lol sounds crazy but yeah! 
Anyone else experience this?