I’ve lost all my friends could I possible be the problem

I’m an (18 m) and a senior in high school. Lately, I’ve been struggling a lot with connecting to people. About six months ago, a big incident caused my friend group to split up. Everyone sided with one person in the group who doesn’t like me, and ever since, I’ve felt completely alone. That whole situation took a serious toll on my mental health, and I’m currently in therapy to work through it.

Right now, it feels like my girlfriend is the only person I really have. Whenever I try to make new friends, it feels like I’m doing something wrong, and they end up leaving or losing interest. It’s made me lose all motivation to put myself out there or even try to build relationships.

My routine now is just going to school, doing my work, gaming sometimes, and going to bed. I’ve never really had a best friend in my life, and I don’t know if it’s me or just bad luck. I’ve always struggled with loss, and I feel stuck. I don’t know how to develop hobbies, make friends, or even start rebuilding my life.

I just really need advice. Thank you to anyone who takes the time to read this.