[Tichy]

In what way do you think you are a bad person? It sounds a bit as if you are carrying a baggage of possibly irrelevant morals with you (as in you don't really subscribe to those morals, but somehow feel bad for that). Perhaps you could simply find someone with compatible values?

Edit: I know several people living open relationships, polyarmory... Still not sure it can really work in the long run, but might be worth a try (both monogamy and polyarmory probably have their own problems, anyway).