Anxious attachment and avoidant attachment?? Help??

So I (F15) have liked this guy (M16) since a little bit after we first started to become friends almost 3 years ago. I was 13 and Avery, my BF, was 14. Well, I thought all chances of us being a thing beyond friends were gone when he mentioned his girlfriend at the time, so my feelings went away. We met at therapy group and the group leader left, and so did he, so that helped my feelings to go away. I thought they went away forever though.

Well, one day, I found him playing a video game on his phone when we were both waiting for our therapists to come. He instantly recognized me and I got his contact information. We became close, and he started developing feelings for me. Well, afterwards, I found out that he had a boyfriend now and asked his boyfriend if it was okay to date me, since I liked him too, but they turned out to be in a monogamous relationship, so I moved on from him and decided to stay friends with him.

However, I always saw him as someone I could trust, as I even did an activity with the therapist I have, saying something like "Trusted people I can talk to: Avery, [name], [other name]" etc.

I am downright obsessed with the guy and I don't wanna be like this. I mean, we finally started dating for real, he's not with his boyfriend anymore, and he loves me. I've been to his house a few times and he's really fun to hang out with. Also, I check my messages every few minutes hoping he texted, he's constantly on my mind, and my feelings for him even come out throughout the day as me trying to be serious and focus, then self-dislike, then frustration.

And I get really depressed and stuff when he talks to other people. It's not so much that he's talking to someone else, that he's focusing his attention on someone who isn't me, but moreso that he leaves me on seen/opened constantly and doesn't reply. If he does reply, he gives pretty dry responses but that's the kind of guy he is. He's always been a bit of a dry texter and has always been less of a texter and more of someone who will just acknowledge your texts.

Deep down, I know he loves me. I just don't know how to deal with my emotions towards him, but I'm trying. I'm lowkey worried I'm becoming like one of those anime "yandere" type characters.