Have you talked to your midwife about it? It may be helpful to be on all 4s when your birthing time begins. Or doing inverse positions.

This sounds esoteric, but I'm getting the feeling bub's ambivalence about position is related to your ambivalence about birth - maybe some unresolved fears. It may help you to write them down, go for a walk, talk to bub, then come back and burn them, letting them go.

Bub will end up in the right position for him/her when it comes time to be born.