I need to vent

For starters, my fiance and I have been together for 3 years now that have been rocky. The beginning of this year had been an emotional rollercoaster and had found out that he had kissed my best friend.. The only real friend that I had and he had been texting her, telling her how he was unhappy with me. At that time, he had been working non stop. We did fight and due to me being over protective of him and yet he felt that he wasn't doing anything wrong. He would spend his whole paycheck before paying his bills, and would lie constantly and saying that they were paid... Yet I would find him scurrying around to make enough to get by. I would pay for all our dates, activities and would even give him money. I didn't know how to get him to stop. Then, that's when I found out about how he had kissed her. The worst part, she was the one who had to tell me because I knew he never would have the courage to. I had an absolute breakdown because I thought that he could never go that low. Nothing else had happened but a kiss and he had shown me everything, but there was still the doubt of course. He had become violent verbally in the neglected span and I felt horrible.. When we fought, he would call me stupid, scream at me and just treat me like dirt. I won't lie, I yelled back. Ever since the incident, he hasn't acted the same. He has shown me how much kindness he has and how good he is, showing me how sorry he really was. I have no doubt in my mind about him and I never think he is lying to me when he says that he is keeping his promises to never hurt me again. I have no reason to doubt... (In arguments) His anger is slowly getting worse once again. He had started calling me names (not anything vulgar or like cursing) and had told me many times that I don't know what I'm even talking about in the current situation or that my stupid opinion didn't matter. "Your opinions on this are just so dumb!" . All the while, he raises his voice with everything he says and just sounds completely violent in nature.. Not the man I wanted to marry. Every time I tell him that he hurts my feelings, he let's me know that it doesn't matter and what he says matters. Nothing I ever say matters to him. When the argument is over, he will act as if it never happened... then if it is brought up on how he treated me, he apologizes and agrees with me out of the gate... I don't know what to do.