What would be a good way to confess to my ex?

What would be the purpose behind it? If you're just trying to get it off your chest, write him a long letter letting him know how you feel. And then you have 2 options. You can either send it to him, or throw it away and see if you feel better.

Well, who broke up with who?

The best way to confess to someone that you love them is to tell them, face to face. It takes courage, but you can do it :)

If you broke up with him, tell him asap, it may save the relationship. If he broke up with you, you can tell him to get it off your chest but it probably won't save the relationship. Sometimes it helps to just get it out there, but if he broke up with you hon, you should be more focused on just moving on.

Good luck!