there is alot of discussion here on what I initially see as a very simple solution.
You could very well fit into a poly relationship, the key is a very basic concept of finding the right one. It will basically be a cpl + you and not a triad or more for that matter. You seem very open, self aware of the issues going on with you and based on that alone I would accept you into my dianamic and would be totally fine with you coming or going as you please and allowing you to be as involved or not as you are comfortable with. The key to this thought process is open communication (naturally) but one rung up from normal poly relationships. You have to practice the idea of dedication to the others by/ through your actions. "you dont come over all the time but you dont go into another house either" The ones you are involved with must understand that aspect to you and see that it doesnt mean you arent interested or feel less or that you are just using them to get your jollies off. Open up, ask around, and be up front about it. I dont know if you are a girl or guy but if you are a girl then I would be perfectly fine with the way you are. I find it rather intersting and attractive actually and it wouldnt change my level of commitment or expression of emotion toward you. No need to stress over it too much.