Need advice/opinions

So, I was at a party a few weeks ago, started talking to a girl. Anyway so we talked for over half an hour. It then started to rain so we all left. Fast forward to the next day I message my friend and ask for her Snapchat. I add her later that day. She adds me back and we start talking. Nothing super juicy. So from a friend I found out she has a boyfriend. Now here's my problem, I think im In love, now I am in highschool but I know the difference between love,lust,etc. I've never felt this way for anyone, I get weird feeling in my stomach, excited when she texts back, and anxious when she doesn't respond quickly (And no I am not clingy in general) Anyway last few weeks we've gotten more in-depth, we've talked late. And Large conversations about stuff I've never talked to friends about that are of the opposite sex, even joked about taking a trip down to Florida (she learned I have my license). We almost talk like a couple, hell last night we were talking and she said something about my personality, she said she liked it. Asked her what exactly said she couldn't exactly say but she likes it. So over this time period I've only seen a few indicators she has a BF, one in her snap name she has her first and last initial, and his last. And a total of 3 snap stories with him, including one them out to dinner and she isn't smiling, and at that party he wasn't with her. Now before you say it, no im not trying to steal her from her BF, im not that kinda person. I won't. But I want opinions and advice on if I should stick around and wait and see if anything happens, if I should tell her how I feel, or just leave it as it is, Or just stay friends.

Thank You in advance.