Hmmm although I said I was fine with mono I've done some proper thinking on this today and I don't think I've ever had a relationship which was genuinely monogamous and successful.
1st long term relationship - lasted 1 1/2 years) We had a threesome with her best friend, the two girls also brought different aspects into their friendship and I could see that they were good for each other and that the friend was a calming influence, therefore she was good for us. I was also many of the things she always said she wanted in a man. I dreamed for a long while about becoming a triad, however this was long before I even knew about poly and had no idea even how to approach this subject.
2nd long term relationship - lasted 3 years) Our sex life pretty much completely broke down and we became like best friends who were in a relationship. Conversations relating to sex usually went like this...
I come on to her
She says no
I back off
She bursts into tears
"What is it?"
"I don't know why I always say no"
"OK, well lets try to work through things - are you happy and fulfilled in our sex life? Yes. Do you love me? Yes. Do you fancy me? yes. Do you lust me in a really primal way? yes. Well then what am I missing?"
She would then come on to me
I would turn her down, I don't want to have sex under those circumstances!!
Eventually I would usually broker the peace by asking her to leave the room, get herself a drink, dry her eyes and come back in to treat it as a new situation
For at least half of our 3 year relationship that was it. I tried opening her up to things; I asked her to explain her innermost fantasies and she just said she dreamed of me being inside her - no details, I took her to a sex shop and asked her to explore it with me, I tried watching porn together (letting her pick the videos)... after all that I was out of ideas.
I loved her but my mind was wandering. I came close to leaving her for other women twice but I never did.
Ultimately I became so infuriated with the lack of communication that I went out and slept with a random girl. I told her straight away, I guess a part of me was hoping to spark her into talking. But she treated the cheating as the issue rather than the symptom. 6 months later we split up.
I was gutted by that because she was my best friend (far more than she felt like my girlfriend over the last 2 years) and I really do even now still miss her.
3rd long term relationship - lasted 6 months) Although nothing non monogamous ever actually happened, she did class what I did as emotional cheating. Basically I tried speaking with her about something and she became unreasonable, so much so that she reminded me of my first girlfriend (who as I say needed her best mate around to keep her calm)... anyway she pushed it so far that I decided to end it with her, then she hung up and refused to answer my calls for a few days. Before I had actually got to see her again a female friend of mine had replied to a status on my facebook and before I knew it I was flirting with her and asking her out for a drink. The girl I was about to dump considered this emotional cheating and dumped me.
By contrast since getting into the poly scene everything has felt right. I loved watching B fall for her girlfriend and seeing how happy she was that she could have both of us. I have loved seeing that same happiness in S as she has explored polyamory with me over these last few months. Furthermore it's great to know that if I ever find myself developing feelings for someone then there is potential to see where it leads without that being at the expense of S who I love very much.
I know I say I'm somewhere in the middle of the mono/poly lifestyles but in reality when you break it down I'm probably more suited to the latter. I'm enjoying exploring it and if we can work through the insecurities and renegotiate things with S then I would like to date within the kink scene, and right now there's nobody else I'd like to date other than J.