Cherrygirl, Mono speaks the truth.....it can be confusing and it certainly can be hurtful, too....there's no sense in repeatedly hurting yourself. I really hate that I've put my wife of 27 years thru this transition that I feel I had to make. She's a real trooper though and values the relationship with her friend as she values our marriage. She's making the transition from being totally monogomous to poly and it's not easy for her. For me it sure seems kinda natural (and yes I was totally monogomous throughout our 27 years). I don't know how old you and your guy are, but I do know all kinds of games can be played by people.
From what I can ascertain in my own circumstances, it has to be easier for middle aged M + F to go poly. You're just at a different place inyour life. Less concerned with what society thinks, more independent financially, kids and those responsibilities gone, etc. You also are more likely to realize that your time on this planet is growing shorter and your capacity to love and care for others has grown immensely. It just seems really natural to me. It certainly can be used as nothing more than an excuse for swinging to others. Do what you have to do to be true to yourself.