<human>: Summarize the given text in a few sentences.

This whole story is going to make me sound like a selfish ass so don't be afraid to tell me that I am. 

I've been dating my girlfriend for about a year and things are going really well. We have a similar sense of humor, barely fight. Like similar things (for the most part). She was the first person I had sex with and I was hers. The problems we've been having came to the surface when she started to talk about marriage all the time with me like It's a surefire thing. Especially after a night of drinking. I told her that it freaks me out and she slowed down for a while. But recently came up when she asked me to buy her a promise ring. I said I'm sorry but I won't because to me that's just a word for a cheap engagement ring and I'm not ready to be married to anyone. This lead to her crying in bed beside me for a long time. Which lead to me thinking of spending the rest of my life her and what it means. 

A week or so later I told her that I'm curious about sleeping with other people and asked her if she was. She got really sad and thought that I was going to cheat on her.  I don't blame her for thinking this when I went off to school I did kiss two different girls. Afterwards guilt and unrelated depression put me in the hospital for 18 days. After this conversation I was ask but entirely sure a open relationship was off the table. A few days after this I started an involved conversation about our sex. We've been having sex about 4-5 Times a week and she revealed to me in the conversation that she doesn't like that much sex and it hurts her. Then she started crying because she was worried I wouldn't like her because she only wants to have sex about twice a week. In truth it did make me sad and confused because I always thought she liked it and now I feel lied to and feel like an ass for considering breaking up. Especially with the guilt from cheating. I feel like I owe her not to. This is compounded with the fact that she was raped before dating me.
<bot>: girlfriend wants marriage and revealed she has a lower sex drive. Freaked me out and lead to me getting scared and imagining the rest of life with her. Now I want to sleep with other women.