Yeah, I have met people like that. Especially if you're the type who falls in love easily then they are a type to avoid. I have nothing against bisexuals but will never date one again. Fortunately, as you get older, those people tend to disappear from the scene. So, just hang in there and try to screen potential partners as best as you can. Don't be afraid to ask questions before you go to bed with them. Don't be shy. Write down your questions in advance so you are prepared what to ask. Of course, ask in as charming a way as possible.