<human>: Summarize the given text in a few sentences.

To preface: She has been my first and only love. We lost our virginities to each other and I would consider her my best friend but I can't help but think about what life without her would be like.

We talk about the future a lot and, to her, the idea that we're going to be together forever is a given. She likes to talk about the house we'll live in, the kids we'll have, and the things we'll do but I can't picture myself being completely content if the next 40 years are the same as the last three even though we have a generally great relationship: good communication, decent sex, lots of great conversations.

The idea of living without her makes me sad and the idea of breaking up with her breaks my heart. 

Maybe it's because she was the first girl that I fell in love with and only girl I've ever had sex with that I'm always wondering what it would be like if I didn't go down this path. Since dating, we have become relatively isolated and my social life and social skills have seriously declined. Most of my friend group has moved away while I stayed in my city to pursue school and be with her. I don't even know what I would do if we weren't together. I know I'm young but it feels like I wouldn't be able to experience this kind of relationship again.

She's still crazy in love with me and I still love her. She treats me like a king, always makes me smile, and I connect with her in a way that I've never connected with anybody before. I just can't shake that nagging feeling that this isn't how it should be. I don't want to make a decision that I'll regret for the rest of my life.

Don't know what kind of advice I'm hoping to hear but I just had to get this off my chest. Has anyone experience anything like this?
<bot>: I don't know if I would be making a big mistake by breaking up with my girlfriend. We still love each other, but something's telling me that this isn't how it should be