<human>: A few months ago I got out of a ~3 year relationship and I've been struggling since then to move on without having any real closure. 

Towards the end of the relationship I began to develop feelings for someone else, who was a few years older and in a position of authority over me. When the school year ended we stayed in contact over the summer after my breakup and even managed to meet up once briefly when we were in the same area. I don't think he has romantic feelings for me but I can't get over this crush. We see each other a few times a week now that we're back in school, but we are always in a group of friends and haven't been alone.

Here's where things get complicated. Last weekend I had my first "one night stand" type of situation with an acquaintance of a close friend of mine. Only a very select few friends know about this and I don't really have any plans to see this person again, but until now I've only ever been with one person (the ex-boyfriend) and I don't know what the etiquette is in these situations. 

So in the middle of unresolved feelings for my ex and having sex with a near stranger, I want to somehow start a romantic relationship with a crush who views me as more of a little sister than a future partner. What should I do now?

Can you give me a shortened version of the text?
<bot>: Just got out of an LTR, crushing hard on an older friend, and had my first casual sex experience. Not sure what to do now.