You didn’t ask a question so I’m going to assume that you want some help with your relationship and the lying. First, I think you and your girlfriend should not be living together or moving to something permanent until you solve this problem. You broke her trust — which is the very foundation of a healthy relationship. That is going to take time and a major change on your part to fix.
You say you’ve been lying since you were 10 years old. That’s almost 20 years of lying to avoid having to deal with mistakes you make. I don’t think you can fix this by yourself. If you could, you would have done so long ago. You need to do some hard work in therapy to get over the impulse to lie and to cover the lies with more lies. It won’t be easy. But you’ve already seen how damaging that approach to life can be. Hopefully, that will serve as motivation for you to get on it.
The good news is that you are only 26. Dealing now will set you up for a long life of integrity and for being the kind of person your girlfriend can love.
I wish you well.