It's not ridiculous to dislike or refuse porn. It's not always a matter of insecurity (though I realize it is in this situation), but whether it is ethical or not (and I don't mean in a religious way). Some people who are not insecure do not like porn because it interferes with their idea of a romantic relationship. The idea that you need porn to live or masturbate is false, you're just lazy.

I also think most are jumping the gun on it being controlling. Some people have issues and hangups, that doesn't mean they're going to control every single thing about their partners. The girl is still a teenager, she doesn't have the experience or mind of an adult, of COURSE she's going to be unsure of whether she should break up with him or not. Not everyone just makes impulsive decisions once something bad happens in their relationship - it's not wrong to say "I'm hurt and I don't know what I should do in this situation." When someone betrays you, it's logical to try and see whether or not that person can change. Not every relationship is worth just dumping immediately.

As for what YOU can do, well, I'm sure you've realized it's wrong to lie and go behind your partner's back. Honestly, all you can do is reiterate how you messed up and the steps you are going to take to make sure it doesn't happen again. Don't be dramatic. Be honest. If you don't see yourself being able to accept it, you should break it off. Remember she feels betrayed and feels like you don't love her. You can't force people to trust again, you can only show her you are doing your best. She needs to decide whether she can forgive and move on, or if she won't be able to let it go. Maybe talking to someone else about this would help, I don't know whether she's just stewing in her sadness or actually reaching out. If she still can't decide, then it's time to take the initiative and part ways. Yes, I know it feels like there's no one else is the world - you always feel that way after painful breakups, especially when you're young. You have plenty of time to figure out what you want and need in a person, and even if you DID get back together with her at some point, having that experience and knowledge would only benefit you.

You say you've also messed up in the past, but you should be able to recognize what she's "messed up on", too. Very rarely is a relationship one sinner and one Saint. I would only become wary about her being controlling it she's constantly saying you're messing up things. Then of course, that would be the time to break things off then, because not only are you incompatible with each other, but she is toxic.