I love my partner, but my brain HATES relationships

I'm 34F. He's 28M. We're both pansexual. He says he has no real preference regarding gender, but what he shows says that he's clearly lying. He seems to prefer femboys and trans-women. I don't have a clue as to why he picked me, a Cis-woman, other than he wants to have a big family.

I don't at all think he would stay for one child, let alone more. He doesn't like the two daughters I already had before I ever met him and they're teenagers. I can't imagine what he would think about a baby. I don't think he's ever been around babies for more than maybe a day or so. His family is SUPER against them.

Meanwhile, I had two kids before I turned 21 and I'M STILL NOT GOOD ENOUGH TO HAVE THEM IN MY LIFE. My parents adopted them officially when my oldest was 3. I know I'm never going to be okay enough to raise a child. I've tried expressing this in every possible way. He doesn't care. He just wants kids.

Despite this, I love my partner. He takes care of me and even puts up with my constant mood swings without complaint. I know he very much does care about me. If he doesn't feel anything for me, he's a very good actor. He's very affectionate, loving, kind-hearted, smart, talented... Not to mention he's incredibly attractive. He's been loyal to me as I have been to him. He's never shown me that he'd leave me for any reason, but it doesn't matter what he says. My brain WILL NEVER trust it. My brain has always come up with reasons why relationships won't work. Eventually, it destroys the relationship.

It's probably for the best that I end this. I don't want to, but I don't want to be the reason he hurts. After all, he hasn't done anything wrong.