I haven't read all the responses, just your post. It's amazing to see how badly some people deal with things that I have dealt with but thought it wasn't so bad in the big scheme of things. I've been through exactly that thing in the past many times, did all those similar things, but I never pressed on with it so far as to driving over and "confronting that arsehole" and I didn't write so many messages (but enough to be on the same track as you just did) and I never drink, and I don't do drugs, so I never got suicidal but at times I did wonder if there was a point to all this.

Your mistakes were the same, you just handled it a lot worse. Trust me you have freaked this girl out more than any girl I have ever, and I have zero chance of seeing them again, so you have negative one-thousand chance. So yes, move on. You fix up this fucked situation by fixing yourself and moving onto another girl, cause you fucked this one up beyond recovery.

As for your mistakes, it goes before the break-up. The first key point is her own words, she's "worried you never get jealous". That needs to be addressed. I would tell her I'm not a jealous person, but I would very clearly lay out the ground rules. Catching up with a friend one-on-one is okay. Cuddling up on the couch with a DVD one-on-one is definitely not okay. Because if she tells you something like this it means she doesn't feel very sure of your strength, so she wants to test it. You didn't take the challenge by responding to her in a way that shows you are strong, and instead you made the problem worse by continuing the same way - she talks about a Travis guy and you continue not being jealous.

Usually if you're arguing about stupid things it's her not feeling "safe" with you. And if you don't nip those arguments in the bud, and instead drop down to her level and draw them out, it makes the problem worse, and fuels her fear that you are not strong.

Again if she asks you "did you ever think about breaking up", that's a pretty scary statement, and you're supposed to show your independence here. But instead you said "yeah but we talked and I feel better about it" shows that you'll practically do anything to stay with her. In a subtle way but that's the message.

So yes she started trying things on with this Travis guy, that's why her "phone was off", and you were right in being suspicious, because deep down you knew where this was going, because of your behaviour. The rest is history. I went through the same thing many times, I just never went as extreme with the bad stuff as you did.

Oh and the other mistake after that, which you may not be aware of, is once the Travis situation was bothering you, you tried to stop her from seeing him. That's way controlling and jealous. What you should do is instead tell her how things are; you'd say something like "If you continue down this path, we're going to have to break up." in your own words. This will make her think seriously about what she wants. If she really wants you, she'll come back. If she wants to break up with you, good riddance, you can't force her to stay with you, which is essentially what you were trying to do. And at that point she was quite justified in calling you clingy and demanding. And when she swore to you that they were just friends, it was just to get you off her case so she could try things out with him. And when she told you "Let's break up but not see other people" she wanted to see Travis, or maybe even someone else, but was worried how you would feel about that, since your whole life seemed to depend on her at this point.

And yes that's when your AFC behaviour began but as you can see, you did the wrong thing every step of the way, long before that. Turning AFC at that point just made her opinion of you being AFC into a concrete certainty. After that you just became creepy stalker boy.

Very, very insightful Conker, thank you. I apparently made more mistakes than I realized. You are right, I basically made her my life and got scared when I thought that was being taken away from me. I should have been more independent.

As far as the arguments, you're right again. She would want to argue about the most ridiculous things and I would actually lower myself to her level. I would get stuck on trying to explain where I was coming from and she would just get more upset.

Again, thank you, very insightful.

How could I have responded to this in a better way?

That's great, you seem to clearly see where you went wrong now, and it's only been the one time. I'm glad my experience could help you - I've been through it all too many times.

As for the question, of course it's always better to not get there in the first place. But the reason I didn't give a direct example is because its easier to remember what not to do, and let something else come naturally in the moment. So I can give you an example or two but it's really just me trying to visualise being in the situation, which is not the same as yours. I've never been in that exact situation but I've been in similar ones.

When I imagined it, I find myself wanting to respond with "What makes you ask that?" and open a dialogue about what she feels insecure about in the relationship. Since that seems to be the motivation for such a question. So in saying that, I'd like to emphasise to you that it's important to focus on the intent behind the words, not the words themselves. So yeah I would get her to talk about it, and then based on what she said, I would try to come up with an appropriate reply. So... if, for example, after listening to her, I could tell she was actually getting kinda intent about breaking up, then I would beat her to the punch and say "Yeah you're right, it's probably time to move on" and re-enforce the reasons she gave and come up with ones of my own. Seriously I believe it's better to be a man and accept what's happening than try and "convince" her to like you.
If I detected uncertainty about the relationship (and I would be asking the right kinds of questions to probe this information from her) then I might have a go at addressing what I perceived to be her insecurities, and follow up with doing something fun.

But yeah these are just examples of something OTHER than going "hey no no no babe, we're all cool! Let's stick together!"

With this question I'm more sure about what I already know is wrong, than what would be right to do.