Tell me what I already know

So I've been seeing someone for a while now but lately everything has gone to shit. She was married and left him for me. Which I've always felt guilty about but I tried to be there for her and her kids as much as possible. She's stressed and has a lot going on. But I'm the one who she takes it out on. Lately we fight. Like constantly. The simplest conversation turns into a war. We drive each other nuts. I love her but I can't take the constant fighting. I never know what to say or do anymore. She's a ticking time bomb. I suggested some space, which she's doing but doesn't hesitate to constantly tell me how low she is and how alone she feels. Well I've been feeling low too. She tells me all the bad things then turns around and says I'm amazing. I'm mentally exhausted. And I don't know what to do anymore. A part of me is saying it's because she's got a lot on her plate. Another part is saying maybe I'm just an ass hole and don't know it. And another part is saying she's nuts and just throws a fit until she gets her way. If I call her out I'm being a bitch and hurtful and I'm the worst person ever. I just feel low and I'm sick of getting shit on. Ugh. What should I do guys?