His breakdown is NOT about your past. He was simply due for a breakdown. This guy is a "blamer."

Stop texting him. That's just fanning oxygen on the fire. Discontinue putting energy into something that needs to be allowed to shrivel up. Learn the art of "changing the subject." If your past had been happy and you'ld been in great healthy relationships, then you wouldn't have been available to get involved with him. He's no prize catch himself with his mental instability. You needn't worry overly much about "losing" him. There aren't going to be a lot of takers looking to line up to get with him. He's a self-absorbed baby.

You have a history of falling in love rather easily . . . too easily. (What do you love about this guy?) Hang back a bit and let him seek you out. He's going to keep harping on your revelations. ["How do I live with these images of your past? . . . oh, no . . . OMG . . . oh, no . . . oh, no!" This is nothing but shallow drama. Firmly state that the subject is closed, when he badgers you.

He is very, very immature. You have to be the adult in the room. You have to handle him with a firm hand - setting limits. That's what he needs to feel more secure.