Am I in the wrong for getting back with my ex?

Here's a little bit of context. I am a trans guy and around 7 months ago I met my partner (they're genderfluid). We met of school, but we so happen to go to the same one, they are in the year above me though. We started dating a few days after we met, I know very rushed but i really liked them. We then dated for a month before they broke up with me, one because the relationship happened too quickly and tbh we didn't know each other well and because their family didn't accept the fact that they were dating a trans guy.

Now its been around 5-6 months since we split up and I've had the BIGGEST crush on them, like I've been talking and thinking about them non-stop, and over the past few months they've kinda been hinting that they liked me (always reacting with hearts to my posts, complimenting me randomly etc...) I was confused by this because they had a boyfriend.

The other day (this was at school) they came up to me when I was talking to my friends, and my ex came up to me, my friend (let's call him Mark) told me not to turn around because they were there. My ex then asked if we could have a little chat and I said sure, we went a few metres away from my friends and then they started talking. They confessed that they had a massive crush on me, and said that they really want to get back with me if I shared the same feelings, which I do so I immediately said yes. Honestly I was on the bloody moon, they also told me various other things, which I am also super happy about. They then asked if I would go with them so they could get something for lunch and I went with them.

They then explained to me (while we were waiting a line to get their food) that they have not yet broken up with their boyfriend because they have not been able to find him, and didn't want to do it over messages. I told them that, that's fine. They then said that they're going to find him after they get their food. After they had gotten something to eat, they asked their friend if she knew where her boyfriend was, and she said that she had no idea. We then started walking to my friends, but then they saw her boyfriend so they asked if they could have a few minutes to talk to him. So I carried on walking towards my friends and they were all walking away, I went to them and Mark just turned around, glared at me and then carried on walking off. I immediately knew that Mark was pissed off at me, but I had no clue exactly what I had done wrong.

Later that day, when I checked my messages, I saw that I had lots of messages from Mark, calling me a pathetic piece of shit and telling me to never talk to him again.