we both r in our late 20s. Have a 2 yr old baby. He says it just hurts and doesn't know how to explain it!!! And dryness isn't the cause as we have used loads of lubricants as well.
It very well could be your pelvic bone rubbing him. With the birth of a child, your bone structure can actually change as it also does as you grown older. It really depends on the shape of your bodies and the angles at which he enters you or you ride him. If it hurts, then try switching angles or positions, maybe try reverse cowgirl (facing away while you're on top) and see if that's any better.
There are just some positions that are uncomfortable to down right painful for people so you've got to work around to find variations or different positions that are as satisfying.