What do I do about this situation?

I was dating a boy for 2-3 years when I was 14, he cheated on me so much so I left him. Then I started dating another guy who seeeemed amazing but turned out to be an abusive narcissist. I was with him for about 3-4 years and then every now and then for the next 2-3 years I would go back out of desperation. He only ever got worse with the cheating and physical/emotional/mental abuse. So I haven’t gone back after the last time (after I left I became severely anxious and depressed, lost 22kg, developed a chronic pain condition).

So I started talking to my first boyfriend again. Just out of curiosity. We hang out, all that sort of shit. Now he has feelings for me and says I’ll be his gf within a year. He just broke up with an emotionally abusive girl. I think he just likes me because he needs someone to be around after his breakup. And that I seem unobtainable. I don’t want a relationship, I’m not interested in romantic feelings. I be low key mean to him but I think he actually likes it. I’ve told him I don’t want a relationship now or ever. But he keeps saying he’s going to “break through my shell, pull down my walls”. I don’t have shells or walls. I’m just not down with relationships and all the drama and responsibilities and obligation that goes with them.

What should I do about this? I do like hanging and spending time with him. And it’s flattering that he likes me, but as I’ve already told him, I don’t want a relationship.