I'm a little over your age now, and went through a very similar realization and breakup at 24. I always knew on some level that I was into women, and on a deeper level I think I always knew I was gay, but had convinced myself I was bi mostly because being gay just wasn't an acceptable option (family background had me pretty damn scared to deal with/accept/acknowledge any of it). I ended up dating a wonderful guy who I was with just over 3 years and we lived together for the last year of that. It was while living together that it really started to become apparent that I wasn't quite as bisexual as I might have hoped. We had a pretty good sex life to start but over time it became harder and harder for me to get into it, and I found myself thinking about women more and more. There had never been any one specific woman I was interested in but I found myself constantly getting flustered by attractive ladies at work (I worked in retail), and the more obviously queer the lady was, the worse the fluster was too. It actually eventually lead me to start hanging around this subreddit a lot which lead to me spending a lot of time in the IRC channel (not sure if that's still a thing, was on freenode) and talking to people from here pretty much daily. It was never a romantic thing but just having some gay ladies to talk to really helped clear up my thoughts a little more and I finally accepted that I was gay as hell and needed to do something about it. I knew my ex was seeing marriage and possibly kids in our future and I didn't want that. We still got along beautifully but I knew it just wasn't going to work out, and the more I realized about myself, the more dead our sex life became too.

Finally I decided to tell him, though I was able to secure another place to live first (thankfully, though it was still about 5 days from when I told him to when I moved out). Even though I'd done the breaking up, I was pretty goddamn crushed. It didn't really even fully hit me until I'd moved out even though being there that long with him being just completely cold to me and me sleeping on our love seat (and eventually the living room floor as that was slightly more comfortable) was painful too.

I didn't quite have the same level of panic as you did questioning if I'd done the right thing or not, but literally days after I'd moved out I met someone who I clicked with beautifully and who was interested in me and the excitement of being able to actually pursue that helped calm me a little bit. But then of course I freaked out about that happening so soon after my breakup and feeling like a shit head to be falling for someone else so soon. I lasted about 2 months "totally not dating" that person until I gave in and just started a relationship there. Nearly 4 years later we're still together (side note in case people have seen some other posts of mine around here - we were poly from the start until very recently when I broke things off with another partner and we closed the relationship. That's another story for another day though). It is everything I was certain I was missing before I broke up with my ex and more. Sex is so much better than I ever thought possible before. I was having a lot of the same freaking out have I fucked up thoughts you were having back then but looking back I absolutely know I made the right decision.

My point in sharing this is to offer up someone to talk to if you want to. I can't promise I'll help all that much but feel free to send a PM or just chat here if you need it. There is the difference that I met someone fairly soon after I ended things, and it kind of helped settle my freak out "have I made a mistake" thoughts sooner than later, but beyond that your situation sounds painfully familiar.