[Catharsis.]

From what I've read in your post, it certainly seems like you're doing as much as you can to reassure her, and I encourage you to carry on doing that, as you are, maybe with a little tweaking.

I can relate. Both my girlfriend and I need reassurance from each other quite often with respects to a variety of things I won't get into. Like you, I'm more than delighted to reassure her, and she's more than delighted to do the same for me, since we bloody well mean the world to each other. We were each other's best friends before we started dating, and now we're each other's first loves. And, well, you said yourself you don't expect any quick fix to the situation, and I'm pretty sure there isn't one, as much as I wish there was. It's something that one has to work on for quite a while, to tell the truth.

There are a couple of tips I can give, which you may or may not be doing as it is. Try to surprise her, if you can. Maybe just an adorable text message or picture she'll wake up to. Anything simple. One would be surprised the difference it can make to someone. If you want to reassure her you're not going anywhere, keep reminding her, when you can. Just pop in something about how you never want to leave her, how you'll love her forever, etc.

Overall, it definitely seems like you're doing quite a lot for her, and fair play to you for that. Note that I am not in any shape or form experienced on the dating front, and somebody else probably would have a better perspective. I do hope I helped somewhat, and I wish you and your girlfriend the best!