I feel you. Honestly I go through the same thing. I eventually break off my relationships when it gets too much.
It sounds like you found someone worth the stress tho. Just be careful. I'm not saying she will leave you, but acting like we do is definitely a stress factor for the other person. Maybe vent to another person occasionally will give her a break sometimes when she needs it most.

Something that sorta helps me is planning something special for someone. If you're super excited to share something with her (be it concert tickets a few months in advance, reservations to a fancy restaurant that's impossible to get into, or family event you plan to bring her to) sometimes that little reminder that there is a landmark event you have to stay together for, closer than the looming "forever", helps.