21 weeks and baby still lays low

He's developing just fine according to ultrasounds and my doctor. But he lays just above my bikini line sometimes he'll venture up towards my belly button but not often. Is this normal? It's staring to get uncomfortable for me because he's growing of course but will he ever pick a new spot to lay? I know my uterus is high because I can feel it externally but I never get an explanation as to why he likes to sit so low.