Bi male, never been with a guy. I'm extremely committed to my girlfriend but I want to explore my sexuality.

I've been with her for a few years now and we're planning to get married one day and start a family. We're both bi, and I've brought up the idea of threesomes, or equal-opportunity chances to explore same-sex encounters in a safe environment (ie, we would be 100% transparent, possibly present for the experimenting), and she really doesn't think she can handle the idea of me being with someone else.So that being said, it's looking a lot like I'm just gonna have to suck it up and live my life feeling like a straight guy who just happens to watch gay porn. It really bothers me sometimes and I'm almost kind of scared it will lead to temptations to be unfaithful years down the line. I don't want to "take a break" or anything, this relationship is far too important to put to the side (also, we live together). I'm feeling extremely trapped and regretful I couldn't do this before I met her.Anyone else in this situation? How did you solve it?