How can I tell if I love him?

Ok well Im 15 and the guy I like is 18. He’s one of my sisters friends and I became best friends with him this year and my friend broke up with him and was gonna go to Semi with him but she decided not to anymore.I broke up with my 1st boyfriend which was one of my other guy friends little brother who is 15 and he ditched me for semi so me and the guy I like are going together.. now…well… I’ve gotten to know him better and Im starting to get really really really good feelings about him.. I always want to be near him now… Do you think Im deeply in love with him cause I really don’t know and I don’t want to make the same misktake with my 1st boyfriend and only like him for a day and then the next day find out he’s a asshole already… I’ve also haven’t had my first kiss yet.. this is my other question, Do you think I should just get my first kiss over with or wait and make it special??