Possible live long mental problems?

My girlfriend and I have/had a not so great relationship I guess...? We both have been diagnosed with mental health problems. In the relationship there is a past of physical abuse, verbal abuse, and mental abuse. We argue often argue about I not trusting her. We argued about the trust issue again and I decided I want to break up with her because the situation doesn't seem to get any better. I want to do it because I don't want to treat her that way. I don't want to treat anyone that way. I want to stay together and work it out but I am afraid she is lying. I am afraid that the situation will never get better. I don't know what to do.

What's your diagnosis and what's hers? Physical, verbal, emotional and psychological from whom to whom - or, if mutual, what share as an overall percentage? Plus - deliberate or accidental and inadvertent? And what are you calling physical, mental and verbal abuse, anyway - can you be specific? And is that your conclusion aided by bog-standard commonsense or online information or what she's accusing you of? And if you don't like getting the urge to treat her that way and feel mightily ashamed of yourself afterwards - which clearly you do or else wouldn't be here - then you need to analyse what's going on to *get* you in that state. Is your temper too easily triggered? Does what trigger it, not warrant or excuse your reaction but at least make why you blow your top easier to understand? Are you being deliberately provoked and can't help but take the bait, I mean, albeit then failing to control and conduct yourself like a more civilised gentleman despite that incoming antagonism? Same goes for not trusting her. Does that just make you sane because she's behaving untrustworthy or breaking prior trust, or does it make you scared to trust generally due to past people in your life having caused those wounds as have yet to heal, with her just exacerbating that reluctance? Lying about *what*? We need a lot more specifics than that, please.