I like this girl way too much and I'm actually surprised she hasn't left me yet
Why do you think that she is going to leave?
She just seems too good to be true.
You shouldn't hold the expectation that your partner will leave you in a relationship as your negativity will show up in your behavior with your partner. You should work on your self-confidence so that you do not self-sabotage your relationships with negativity and pessimism. If you can't resolve those issues on your own, it would be a good idea to seek help from a therapist.
Nah, she loves me.
I think that you need to work on your mindset though. You should not constantly think that you significant other will leave you. It is not healthy.