I still sometimes sleep sort of half on mine but it is starting to get a bit big and the baby kicks and carries on if I lay that way LOL.

It's not wrong, just a matter of comfort, the bigger you get the harder it will be to get comfortable on your tummy.

I must say I am not enjoying this sleeping on my side business, I have to get up because my hips ache so much, even with a pillow between my legs.