Am I making a mistake?

In May 2014 I start talking to a guy from my home town online. It seemed perfect, he was sweet and not too controlling like ex had been. We got along good and saw things pretty much the same way. About a month in I found out he had lied to me about "falling asleep" and had been out at a bar drinking (which he had previously told me he didn't do anymore due to a dui). After that I noticed that he would never post pictures of us online or make any effort to let it be known he was in a relationship. Finally he posted a picture we had taken at Church just saying he had gone to church. I later found out from a girl he had been asking to come see him at work that he told her I was his cousin.

As time went on, things only got worse. He started controlling me. He wouldn't let me go out to the movies with my friends or family without a fight. I would find out from girls (and he would later confess) that he was talking to them and asking them for pictures, having accounts I didn't know about and a lot of other things. New Year 2015 he told me he was at church with his mom who's birthday it was and who had recently beaten cancer, I found out he was really at a strip club. I started finding out more and more that he had been going out partying. This on top of other personal issues sent me over the edge and I made at attempt at taking my own life. The day after I got out of the hospital (where he didn't bother to come see me) I found out he had had sex with another girl. I suspect she wasn't the only one. He had also bought her a valentines gift, even though he hadn't bought me anything the whole time we had been together ( I had spent plenty of money on him).

We recently moved in together, a month or so before he had asked me to marry him. He had been making an effort to call me every night so I knew for sure where he was. He had even been coming to see me which he had never done before. Even now he is great. I work nights so I am always tired and he cleans and cooks for me and things like that. I have access to all of his account and everything but every day it eats at me. All the memories won't go away and I question if I am making a mistake... I just need some opinions. Can people really change? I know he doesn't deserve me, but could there be a happily ever after?