As i read your post, it sounds so much like things I have said/posted in the past – I can relate to being “slapped in the face” – you cant even believe what the cg did bc you *just* talked about it and they go and do it anyway. It is frustrating and makes you feel like you are going crazy. WHich leads me to your “doubting myself” comment – because yes, when they do something we said we objected to, the addiction tried to twist it around so we start to feel like we are the ones in the wrong “what could it hurt? it’s only a little money..” etc etc Making us feel bad (at least in my case) and some times relenting and giving in. This just makes everything get worse in the long run.
It is so hard to stand your ground but you must. For yourself. Last time my cg did something like this (2 days ago!) we talked about it and I told him I would not be treated like that. If he wants to disrespect me I can’t be in a relationship like that. I have gotten to the point where I have said if he acts this way he needs to leave. This is a big deal for me and surprisingly my cg is really trying hard to gain my trust and change himself. And I think that is partially due to the fact that I told him I couldn’t – wouldn’t put up with it anymore. My story is a little complicated (all in my posts if you want to catch up) but the thread is the same – they act out, we protest, they cajole, we feel guilty and bad about ourselves and confused. It is painful, heartbreaking and demoralizing.

Like Monique and velvet said, taking care of yourself, finding support for yourself are very important. It sounds like a silly pollyanna thing to say, but it does really help. I have found posting and replying to others posts very therapeutic as well. It is nice to be understood and not judged.
I just wanted to say I hear you and encourage you to reach out to anyone (real or in cyber-land) who you think could be supportive of you. Just talking to a friendly ear is cathartic in so many ways.
With love