Need help finding this story

I read this story along time ago, not sure how long ago but it was before I had a literotica account. So, I couldn't add this to my favorites or anything. Anyways, the premise of the story is a little blurry to me but I remember a few things. First was the main character, I believe she was pretty young - college aged - and she was at a party, birthday party (maybe her own). I don't think she was enjoying it, or maybe it was over, I don't know. Whatever, so she steps outside to see her older sister's boyfriend (may have been ex's already, but I think at this point they were still dating). Blah, blah, blah, skip ahead and she's at this apartment and having sex. She's a virgin. I don't remember much after this, except I do remember the guy buying her a guitar. He was talking to a girl to get a deal on it the other girl ( the MC) was jealous because it looked like he was flirting with the sale's lady. The love interest is also pretty controlling. There are several chapters (five, if I had to guess) and its put into single chapters with different names, so it doesn't look like a chapter story. That's all I recall, hopefully someone can help me find this story.