I feel like I should end it but I don't want to

I haven't been happy with my boyfriend lately, he's been treating me weirdly, takes hours to respond to my texts, and only changes his behavior for a few days when I tell him it's bothering me. The past week or so I find myself sad to be talking to him instead of happy because of some of the things he says. I seriously don't know what to do, I've never been in this position. We've been together for around 2 years (he broke up with me once in between) and we're 18. I love him so much and I'm tired of saying over and over again that his behavior is bothering me, I feel like I'm constantly nagging/annoying him. This is the first time I've ever felt like this with him and I don't know what I'd do without him. Please help, I'm so upset and confused 😭