Sex on your belly, what’s everyone’s experience

I am almost 28 weeks and often we end up having sex with me pretty much flat on my belly and him behind/on top of me. I am pretty squished into the bed but it’s still the position that feels good. I’m having trouble finding information about whether it’s actually bad to squish the belly on a soft surface like a mattress. obviously wouldn’t do it on a hard surface like the ground. I’ll ask my OB at next appt but has anyone asked their doctor about this?