Feeling like trash.. could someone please help put things in perspective?

So there's this boy I met about a month ago. It was at a party, he was drunk and flirting with me. I was COMPLETELY uninterested and more into his friend. Then I found out that this boy went to my school and for some reason I developed an interest in him.. one day I texted him and asked him if he wanted to take me and one of my girlfriends somewhere (he has a car, we're in high school). He said sure. So I introduced them the next day and he texted me that day saying "Your friend is hot" -.-. I wanted to convince myself that I didn't like him in that way at all so I somehow told her this and she said she thinks he's attractive too. Since then, they've been texting, calling and even having midnight "visits" with one another. On some level, that has always bothered me. She keeps telling me how she has no feelings for him but just wants a boy she can make out with. I tried to just put all these feelings aside UNTILLLL YESTERDAY. So yesterday we found out that he slept with a girl from our school within the same week he was having these midnight makeout sessions with my friend. I called him up and yelled at him quite a bit (mostly because the girl he slept with is also a friend of mine, she's 4 years younger than him and he completely used her). He didn't even CARE, it seems like and this is bothering me so much. He bought that first friend of mine chocolate and begged and pleaded for forgiveness. Me? He told one of his friends to "calm me down". WOW. Today he asked my friend/his "girlfriend now", "Ask Sophia if she's mad at me?" while he was on the phone with her and she was talking to me on IM, when I said "I really couldn't care less", HE LAUGHED. -.- I'm very moody today and all this on top of it is not making things any easier. I just hate feeling like this.. like nobody values ME. Nobody cares if I care or not. :( Honestly I'm seen as the fun, feisty one and this whole rant is very unlike me but I just feel so down... what should I do? I want to cut this guy out of my life COMPLETELY but I want to keep getting close with his circle of friends and maintain my friendship with his "girlfriend". HOW IS THIS GOING TO HAPPEN?