six months and no 'girlfriend' label yet.

About a year ago I realised I really liked my best friend. He's funny and kind and is the first person to ever truly get me. Other than a few weeks when we were living in different cities, we haven't gone more than 3 or 4 days without seeing each other for more than a year now, and there's always easy conversation, new things to go and do etc. It's just easy with him.
I told him I liked him around the beginning of June, and he told me it was a bad idea. The whole catch with him is that he wants to move to Japan in two years to teach English. It's a thing he's determined to do, and being his best friend and wanting what is best for him I could never ask him not to go. 
We both had to move out of our student houses at the end of June houses after spending our workless, lectureless time stuck to each other's sides, going to the pub or simply sitting in with a movie. I basically moved in with him for that final month, and shared his bed. No funny business went down it was just a bit of cuddling, which he dismissed by saying he slept better with someone else and that there was no point in me using the sofa or going home if we were going to immediately meet up the next day. I didn't complain, I've never had a relationship before and the cuddling was comforting and addictive. 
I went home for July, started a new job and he moved back to his parents house whilst he searched for a job and a flat in my city. I was searching for a flat too so I didn't have to live at home. We didn't see each other for three weeks because of my work schedule but then he got a train over and we spent the entire day out at bars and exploring the city as we always did. He ended up missing his train home so I brought him back to my parents house. I was 21 at the time so they couldn't comment on the fact I was sharing a bed.
That night he started kissing me. I had no idea it was coming. Nothing else happened but we spent the night just wrapped up in each other. Afterwards I was sure it was just down to the booze. But it happened again on holiday in Cornwall with our friends. We ended up sharing one of those tiny single beds caravans have, and all our close friends found out something was going on. 
Gradually this became routine and once I got a flat and he started working in my city things got easier and he stayed over more. Eventually it led to more than kissing.
I got brave, with the help of a few pints, one evening and confronted him and he told me that he adores me but there's a deadline on things and that he doesn't mean to keep things secretive but he doesn't want to get super serious and break it off for Japan. He's also a super cynic after too many girls fucking him about and breaking his heart in the past. 
I feel like we're in a half relationship. Everyone knows but he refuses to say it out loud, we spend at least two nights a week together at this point. 
I'm sorry for rambling, I doubt anyone will read this far.. I'm just in love with a man who won't call me his girlfriend but goes out of his way to spend what little time he has with me. He's sweet and kind and gentle and wouldn't do anything to hurt me on purpose but I just feel like an idiot because I just want to be able to say I'm in a relationship without feeling weird about it, feeling like it's this big secret. 
Again I doubt anyone will have read this and I've left stuff out because it's too long but any advice would be appreciated..