Should I breakup with my boyfriend?

I’ll be honest with you guys. I made this kind-hearted boy suffer a lot. He was very depressed in his relationship because he had so many issues with his girlfriend (according to him, they’d break up at least twice a month since the previous year—do the math: 26 breakups in a year, thanks to toxicity on both sides).

Above all, the girl was a bit... "sensitive." She used to hurt him by saying things like "I'm so tired of this," "leave me alone," "I wish I'd never met you," "you're the worst thing that's ever happened to me"—the kind of stuff you'd hear on a melodramatic soap opera. I don't want to downplay her feelings, but she was really cruel at the time and left him traumatized.

Anyway, like any friend, I tried to help him. I went with him to therapy, and we were constantly on the phone. And surprise! he suddenly """fell in love""" with me. And I don't know how to say no.

Unfortunately, I made the mistake of kissing him just three days after his breakup, though I came to my senses the next day and ended things. It wasn't until May—when I felt bad and thought I was truly in love—that I apologized and asked him to be my """boyfriend""". Another mistake.

He’s a really good friend and boyfriend, honestly. He writes me letters and tries not to be too intense with me; he’s a total gentleman. We like the same things and share the same sense of humor, but... I’m not in a good moment right now.

That’s where the dilemma comes in. I’ve said this about him before: I’m never ready for him. That’s a pretty lame way to be. I’ve bought him gifts, I’m attentive, and I try to listen to him, but I’m tired. Above all, I’m overwhelmed. Things from the past are still eating away at me, and my relationships with other people aren't helping. I feel genuinely lonely.

I don't know how to handle a relationship; I’m still just a clueless kid, really. I have a lot to learn about life, but honestly, I don't think things are going to work out with him. In a relationship, you’re supposed to move forward together, but I feel stuck. You’re supposed to feel secure, but I find myself lying to him more and more, or avoiding things.

I don't want to hurt him; we moved too fast, and now I don't know how to put the brakes on this situation. I need your advice—the honest truth—and suggestions on how to handle this incredibly stressful situation, which is genuinely causing me chest pain, fatigue, and a sense of apathy everyday in vacation :,(