Can I ask why this title is so important to YOU? Is it so you can label this guy to others i.e. referencing to your friends that he is your boyfriend? Is it to get clear that he isn't just a fuck-buddy but more important from a relationship point of view? Is it a mental thing so you're more clear of your situation?
I know placing labels on people has it's important but want to better understand why it's actually important to you.