Oh my, where do I even start?
As someone who has been on the receiving end of this, please know that it does not feel good to bel used to, it really erodes trust at a very deep level and you are essentially being disrespectful to your partner and you are assuming that your partner cannot handle the truth, which in many cases, being transparent and honest about your feelings could actually not only save your relationship but also it would allow you to go deeper.
That said, please stop reading if you are together with an abusive fucktard, dump the mofo and take some time to heal from this.
If, however, you are a fairly normal human being in a workable relationship and the monotony if married life (with or without kids) has gotten to you, read on! If you believe to be with the love of your life, please read on even more so.
1.) Trust that your partner can handle the truth, it will make you feel closer. I‘m not saying this is an easy thing to do, but by all means, avoid beating around the bush, especially if your partner has suspicions already.
2.) After the talk, give yourselves some time to see how you feel and by all means, grow the fuck up and start insisting I monogamy, especially if you are hardly having sex anymore anyway.
3.) Think about what you are losing, especially if kids are involved, if you simply dump your partner. Yes, I know, a lot of positive things about your partner are hard to acknowledge in the throws of the everyday wind-and-grind, monotonous life most of us get stuck in, but you know what!? This person is actually showing up for you, all of you (the good, the bad, and the ugly!), so you oughta just kiss the ground your partner walks on, seriously! Anybody can be infatuated with somebody else, chances are the new will eventually wear of and the good, the bad and the ugly will show again, on both sides.
4.) If you feel like you have a good thing, a good partner, to begin with, please stop day-dreaming and wake up, true love is for real and it isn’t always easy. So if you are good together, talk openly about your crushes, don‘t sweep things under the rug. If you can handle it, open up the relationship, it may just back-fire in a positive way and make you realize what you‘ve got at home....or maybe this is what you need in addition to what you have at home. Bottom line is: deal with it openly, assume responsibility for your actions, behave like a grown-up and treat your significant other like a grownup.