Worried about baby position


So you probably assume from my post that I'm a first time mom. Well this is actually my third baby. So I was wondering if it's normal for baby to constantly be extremely low. Like barely above my pubic bone constantly. It's a boy too I don't know if gender matters or not. My first two babies were girls and were in my ribs from about 20 weeks. Anyways, him being there is constantly causing me back pain and making it hard to sit without reclining pretty far. He also like to roll in a ball pretty tight and my lower stomach feels rock hard. I'm only 20 weeks so I didn't know if this was something to worry about. I'll ask my doctor too of course I just wanted to see if anyone had experience in this