I want to break up but don't know how

I legit want to break up with my gf. Things feel very off btwn us and I have no trust in her. I honestly feel like hiding and lying comes naturally to her. However, I'm stuck in her house and I work with her.

We've been on and off now for 2 yrs bcuz I can't count the first one bcuz in her words we weren't official since she was still talking to her ex behind my back. So..anyways...Since then I haven't been able to gain that trust back bcuz she does and says things that trigger me in the worse way.

I just don't feel like we are for each other and when I'm not with her... I find myself a lot happier and less stressed out and my confidence a but higher bcuz I'm not thinking of her.

If I were to break up with her...she'd make it hard bcuz she would just show me the attention and appreciation that I was wanting in the relationship.

I'd rather be alone; she goes back and forth tho:: EXAMPLE: She'll say something along the line of: well the good thing is I don't have to stay here and I can just walk away from her.

THEN I'D SAY THIS:: Well the good thing for you is you can break up with me if you don't want to be with me instead of ignoring things that need to be said to push me to do what you can't do.

So things like that happen...I wish I could write a book. This situation sucks and I wish I never put myself in it. Dating a girl for the first time has been the worse experience ever when it comes to my heart and mind.