Don't want to be that guy, but 2 things wrong here.

First, jealousy has NO place in a relationship. If you're jealous, you never had them in the first place.

Second, never, ever, let a controller into the relationship. It's 50/50, or nothing at all.

With that said, you shouldn't have talked to that person in the first place, especially in any way that would be considered "cheating" or "hiding" anything. That parts unfortunately on you. Yes you are very young and don't have any experience in the real world of relationships either, but we all learn with time.

Idk your particular history with your girl, but here's some food for thought. Find someone who is on your page, has your back, and loves you unconditionally. Someone you enjoy your time with. Interests don't need to be an exact mirror either learn from each other, but most importantly, be kind, honest, and love one another.

Ultimatums are a big red flag. If you hear one, run, unless it's a major issue, crime, endangering each others health, whether emotional or physical, or anything along those lines. For example, I'm an ex-addict, 5 years into recovery, and my wife and I are best friends. But we agreed that if I were to even slip once, it's over. Not good for her or the kids. That alone keeps me clean.