Ashamed

I had been official with my boyfriend for 2 weeks.. we had been dating on and off for 7-8 months prior. I love him. 
One night I went out with my best friend to hang out with her crush (to keep her safe). I was planning on inviting my boyfriend but he had a lot of work and deadlines to attend to and my friends crush said not to invite anyone else. When my best friend and I got to her crushes place another guy friend was there ( a mutual friend). 
We drank glasses of wine and watched movies for a couple of hours. I didnt know how drunk I could get from wine. I debated calling my boyfriend to get me but I didn't want to leave my best friend there by her myself with two guys. 
One thing led to another and me and the crushes guy friend are in a room talking. I tell him about my boyfriend and how I just told him I loved him.. I also told him about something personal that we went through ( I don't know why maybe alcohol). 
For what seemed like minutes I woke up to the sun and a lawnmower from outside his window. I remember blurry images of the night: kissing and possibly sex. I woke him up and asked him, "did we have sex?" But as I asked I saw the condom on the floor. I was shocked. I felt bad but then also numb because I couldn't remember what happened. I know I cheated...
I told my boyfriend-- he is hurt & im afraid I broke his heart and my own. He broke up with me and then with much conversing he is giving me another chance. --I love him and want to be with him for as long as I live. 
Should I be feeling as guilty as I do? 
Should I feel like I'm being selfish in fighting for the relationship? 
...just want outside perspectives-- thanks💕
-disclaimer-- he knew where I was and with whom.. he had the address and everything.