21 Weeks & Sleeping on Stomach

I have a decent bump, especially when I lay flat on my back ... I'm naturally thin so the bump is definitely cool to see, it's like a little mountain or something lol. Anyway, I notice sometimes I wake up sleeping on my stomach. It doesn't hurt, and baby doesn't kick as if in displeasure. Is it normal to not have difficulties with stomach sleeping? I mean, I'm sure eventually, I will stop. But it's not exactly something I can control in my sleep lol. Is anyone else still sleeping on their stomachs? I also still haven't had any issues with laying on my back.