Had baby lye on its side most of last part of pregnancy. Found out had heartshape uterus. Is that why?

Possibly. Some babies are transverse (lie with the belly or back down rather than the head or bottom) in normal uterus. But it is more common in women who have a heart shaped uterus (archuate uterus).
YEs. The presentation of the baby can be related to uterine shape and anatomy.