Dick doesn’t go in all the way? Car sex

My boyfriend and I have been having car sex a lot lately. We try to find other positions to do but there’s not much. He likes when I’m on top but when ever he’s sitting up and I’m on top facing him he says he feels like his dick isn’t going all the way in but I go down as far as I can? Idk if that makes sense. When I turn around and ride him while he’s sitting, he loves it but I get tired too quick when I’m turned around bc of how my my legs are positioned in his car. 😂 He said on a bed when I’m in top he does feel it go all the way in. Are we not positioned right or something? Does anyone know or have experience?