A relationship isn't supposed to be a drain on you. You have suffered emotional abuse already so that can put you at risk for engaging in another relationship that can once again result in your being emotionally manipulated. Often being afraid to express your feelings comes from experiencing another person or persons that failed to consider and respect your feelings and treated you badly for having feelings.

It's important to understand what this guy means when he says he is not monogomus. This means should he find himself attracted to another female, he will expect you to go along with it while he persues a relationship with this other person. So basically this means you are required to live your life around his needs. Considering your history that isn't a healthy thing for you to do. Instead you need to experience someone that can actually respect your needs and feelings.