Where is our relationship going?

I want to lay out a general outline of my relationship with my boyfriend, and I want to know some of your opinions on how our relationship is and where it might be heading. We have been dating for about 3 years now all through high school. It's been the main source of happiness in my life to be honest. He started out being very naive and he didn't know a lot about the world (he was 15). He's changed into a more mature and knowledgeable person now. I've always had problems with bitching about things that upset me (pretty common) and he's always had problems with communication. We've been trying though with those issues and it's getting better. We are together every other day and we enjoy it each time, but he has a history of feeling like he's with me too much and needs more time for friends, work, and family (very understandable). I get that and I give up time with him for those needs. See, I don't see any outside family, a car to get to a workplace, or many friends (I'm a bit antisocial). That's why I want to be with him so much. He's all I have really. In the past, he broke up with me (only lasted 6 hours) because he felt like he was confined and wanted to explore other girls and date other people. Later, he told me he was confused on what he wanted and didn't want to be with anyone else but me. I know I gotta cross that bridge sometime, right? I'm sure he's going to have to try sleeping with someone else sometime. Him trying to date someone else would break my heart, but we are still young. 17 and 18 right now. I have eyes only for him in every way, so I don't worry about that. We'll be graduating next year and we are thinking about getting an apartment. Based on other peoples' relationships, how do you think this one stands? Is it just a high school sweetheart situation that will pass? I don't want it to be because it will be so heartbreaking. All feedback is highly appreciated.