How can a single woman be positive a man is not bi-sexual or gay or a swinger?

If he is gay, he will likely not be interested in you. If he is a swinger, he will ikely try to get you involved. The most important thing is to get the know him and trust the feeling you have about whether he is trust worthy. This is the most important consideration in a relationship and should not be taken lightly if you are making an emotional investment. If you have doubts, you are likely right. I have a private detective friend who does relationships who I ask "How many of the people you check out are cheating?" His answer: "All of them, trust you feelings". Go with your instinct, trust yourself. You could just ask but he may lie. Talk to his friends , family, his ex maybe? But this would only apply if your instincts have been good in the past. If he has healthy sexual urges, then he is probably not a sexual deviant. Just talk to him about it. You just need to be open and honest with each other. You cant control your feelings or your sexual preferences in life, nobody chooses to be gay, straight or bisexual. So just talk with him sometime and be open about your thoughs (not judgemental), he needs to be comfortable and feel like you arent going to judge him. Just leaving him will not answer anything, Everyone has a freaky side to them.... Just make it comfortable...