What do you call someone you been seeing but not made it official yet?

I been seeing someone since last month. We been on dates. Talk every day and been sleeping together. We're not officially together yet. He wants to wait until hes done with university which he graduates April.

Have you been seeing someone for a while and actually worked out? He asked you to be his girlfriend. What do you tell people he is for you if you been seeing eachother but haven't made it official.