We get into a piddly argument and he threatens break up. I'm thinking its because I broke up with him once, and that lasted 3 months. I think he is trying to pay me back. He never means it. I think its very childish for him to hold this over my head.

You need to be unaffected by it. If he threatens something like that, you have to win with maturity.

"Oh, well, I do hope our relationship is stronger than THAT. I know it is for me. Just make sure whatever you do is honest and I can live with it, OK?"

Always calm, always sincere, always attentive.

That's a good suggestion, thank you. I will do that.

It is just a scare tactic He figures you will back off and comply with him because you will fear him leaving if you don't.

Scare tactic and simply fire back with "if that's truly what you want, i love you enough to give you what you would like"

Great suggestions guys. Thank you.