Yes, I've soft-pedaled it up til now, but I believe she is insane. You need to get it through your head that the winner in this little game of "Let's you and him fight over me" is actually the loser. Any man who tries to spend the rest of his life with this woman will suffer constant emotional torture. You will certainly do better by finding a different woman to spend your life with.
I know you enjoy the sexual athleticism. But don't believe that she is the only woman with a healthy sexual appetite. Plenty of women like sex and want it several times a day. And most of them are not trying to fill a cavernous emotional hole with sex.
I do worry about the baby. But with her history of miscarriage, she is still a long way off from being a mother.