Replying to Girl Help! Please (mostly for the females of NS)

My situation is an awkward one. I am 17 and i am a junior in high school. Around the begining of feburary i started fuckin around with this girl (senior). It started just strictly sex no strings attatched (or so i thought) but i never really liked her i thought she was kind of awkward, she has a cocaine problem and she is incredibly insecure. I started to talk to other girls and i could tell she had the feeling i was. on Friday i took this other girl out to dinner she is a sophomore who has a reallly good sense of humor, is nice and she doesn't drink or smoke or anything i also really truely like her so i told her about the other girl and told her that i wanted to break it off with the senior i just hadn't told the senior yet. Friday was fucking amazing we went out, went to my house, i asked her to prom, she met my parents and hung out it was really fun but we went to a party later and the other girl (the senior) was at the party. i noticed the senior and her freinds staring me and her down so i took her outside to talk and end it. While i was talking to her, her friends apparently came up to the sophomore and were calling her a whore and alll this shit while i was outside and couldn't defend her. While i was still outside she came out and told me she was leaving ( i still had no idea these girls almost made her cry untill later that night) so i let her leave because i didn't want to force her to stay but she told me i shoud talk to the other girl and she told me that she still liked me. i broke it off with the senior for good and my freinds were all like ya you're the man and you're a pimp because i was gettin with two girls but i felt like shit about it so i went home. While i was sleeping the senior girl and her friends egged my car which i actually wasn't that mad about and i kinda felt i deserved for leading her on and not telling her about the other girl until she sees me and her at the party together. i just thought it was really immature. i called the sophomore on saturday night and she told me she wants to take it slow and she said she feels like she shouldn't fuck around with guys for a while and time is what will fix it. i told her taht i wanted to hang out with her still even if we werent' hookin up but i feel like im loosing her and i feel like she doesn't want to hang out with me anymore and i really dont' want taht to happen. If any of you have been in this situation or something like it some advice would really help. I am not a dick and i am very sincere but i made myself look like a dick what do i do?