When is a relationship over

Just wondering in your opinion what are clear signs of a relationship coming to a close. Been together 6 months (I’m 16). It’s quiet long distance, 30 mins apart by car and neither of us drive. We meet up like twice a month. We don’t get jealous of each other and we don’t mind when one of us goes out without the other (which I like). Sometimes he says stuff that annoys me like saying “wow ur cool” sarcastically and I know it’s a joke but I always get annoyed. He makes me mad a lot but i think he does it on purpose cause he finds it funny. We don’t have many common interests and the other day I felt a strong chemistry with a person I’d just met the more we talked, which just shouldn’t happen when your in a relationship. But there’s so many good things about him he’s such a nice person he’s wasted on me. I don’t know whether I wasn’t ready for a relationship or if I’m just not a relationship person but I don’t want to be the one to end it. All these years being single talking to boys I just wanted a relationship but now that I’ve got one I almost want to go back to the days where I would get excited when I got a text from a boy or talking to stranger I found attractive. I really don’t know where my head is at he is a perfect boyfriend but I’m not the perfect girlfriend.

I wish he would cheat or something so i would have a good reason to end it