Please help. This is what happened ...

I was dating this guy over a yesr now and in may, of last year, he asked me to be his girlfriend. I accepted. He dated for 8 months and well, things started to get complicated. We gave it a couple of tries, but I felt like it was more me trying than him. 
After recieving X-mas presents, he decided to end the relationship to "get himself back together". 
Time past by and well, we were still going out, and having intimate moments, etc. but what I didn't know is that he was seeing someone else at the same time. It was so hard form me because this was the man I wanted to marry. We talked about it so many times. 
Anyways, he kept seeing her behind my back and telling me that there was nothing there. I believe, until oneday he faced me and said he had kissed her, well, that she kissed him. In the end he said he loved me and that he would always love me. So I, dumbass, let it go. 
He continued to see her, even when he had said he loved me, ee wanted to be with me, and much more.
One day, we decided to have a dedep talk. We agreed to talk at night, to give each other time to think about everything that we needed to say, but when night time reseached he started to ignore my text and calls. I started to get worried so I decided to go look for him. 
In the end, he was doing great, he was with her, on front of my apartment, kissing her, having her in between his legs. I stood there for like 5 minutes and realized how dumb was I to be standing right there watching him with her. Waiting to see if we would stand up and come to me. 
In the end, I ended up slapping him. He cried and said the same things, that he loves me, he wants to be with me, and so on. I cried so much, and well forgave him. 
When the sun came up, I asked him, "Did you mean everything that you said last night?" He looked at me, deep stare at me, ans said "No, I don't love you, I don't want to get back with you, the love making meant nothing to me, and I really don't care about you" 
I cried so much. Still today I cry about it. 
I guess what I'm trying to say/ask to you ladies is, What is you're opinion on this? What should I do? Please ladies, help me open my eyes. This happened a month ago. I haven't spoken to him in 3 days, thats the last time it happened. 
What kind of situation have I gotten myself into?