We are at that age now, my boyfriend and I, where (among other things) the term “boyfriend” should not be unacceptable. I should start over and call him my …what? My partner? We are not gay or living together so that seems misleading. My fiancé? He did surprise me with a lovely diamond ring but it came without a proposal for marriage. I could be more hip and call him “my honey”, “my man”, or “my guy”. None of those feels quite right or very wrong, unless we are in casual company.
In Italy, people of a certain age use the term “fidanzato” or “fidanzata”, which signifies a serious relationship between two adults without a declared path to the altar. Do we have an equivalent in English? None that I’ve found. Help! What are the rest of the grown-ups doing?
accidental goddess 
struggle with the same thing,,, i resort to SO when in a bind
Here in San Francisco, it’s always correct to say “partner.” Details get filled in as people get to know the two of you. I agree this isn’t great, but it’s the best the culture has been able to come up with so far. Culture is always evolving, so something better is sure to turn up eventually.
In arranged marriages in India, it’s always the “boy” and the “girl,” no matter how old either party is–provided it’s a first marriage for both of them. Which gets to be very funny at times, though that’s very much the wrong attitude.
Try out Mr. Big. It worked for Sarah Jessica Parker.