It sounds like you have a great relationship but your heart isn't in it. If that is the case then your partner deserves total honesty. He also deserves to know that you aren't faithful. He has the right to have a relationship based on total honesty. If you are in love with him then you need to get help in how to end such impulsive choices. If you are just allowing the relationship to serve as your safe place but you want other guys then you should not waste anymore time pretending to be in a relationship. If you think that your desire are more of a sexual addiction then you should seek help for this problem.
You have to decide why and if you want this relationship. If you do then you have to behave within the boundaries of a monogamous relationship. If you can't do that then you don't want this relationship. You can't have it both ways. The relationship can't survive with such behavior going on behind his back. The true choice is really yours because you know what is going on at all times. I would make such very serious choices this week.
Please press accept this is the only way I am compensated
Thank you- I've considered asking for an "open relationship" but I know that I woudln't be comfortable with that myself.