I've been in a very similar situation to you - differences being we were the same age, we were together for 5 years (we broke up), and I'm the girl (the one who broke it off). Moved to a big city, I lived in his apartment, I had no nearby home. ( I am now renting somewhere in the city - and I am doing pretty fine ... ;) hah! ).

Anyway. During the relationship I would always doubt if he was "the one" - but always stopped myself, thinking it was just the "grass is greener" demon inside. We were also of different types of outgoing. I wasn't really allowed (emotional blackmail) to go out with friends, etc. In the end, I realised I was just scared of being alone, and had no idea what my future would hold - will I ever meet someone else, will he be nice (my ex was lovely ofc), etc. I realised I still had friends, and we will all make it through somehow, even if you see nothing in the near-future. I broke up with him that same week. And it was tough at first, but I quickly realised it was a good decision. I found myself again, my friends again, and there was nothing to be scared of really. I just had to do it to see it.

I'm not going to tell you to break up or stay together, because I have no right.

That said, my advice would be: you need to spend a few days alone with a clear mind and analyse what your main concerns are about the consequences of the relationship ending. Eg: What will be next for me? What do I do now? OR How will she react? What can we do?

I figured if my concerns were more about myself and my own life (friends, family, self-contentment) then I was ready to be out of this relationship - it would seem I was not concerned about "salvaging the relationship" anymore.

If I had thought "how would (s)he react?//WHat could we do?" Then that would imply I was more concerned with the relationship, and perhaps I would not be so ready to move on, and still see hope.

Anyway, sorry for long reply. Good luck, and you will always make the right decision, as long as you make an honest decision. Be honest with yourself, it's the least you can do for both of you.