It is different for men and women. Women will convince themselves that they love a man they have sex with or they might think they are loose. Love doesn't automatically create great sex. It would be easier to explain the theory of relativity. It is amazing that divorced couples that can't even live together anymore continue to have sex.
Some women can get pregnant simply standing downwind from a guy.
If semen is deposited anywhere near the vaginal opening, then those little guys can swim up there. Don't ever trust a guy that says he can pull out in time. Martyrdom is an empty pleasure. You can try talking to this non-giving guy, but you need to exercise some control over you and this relationship. Bisexuals, by definition, are people who can take sexual pleasure from either sex.