I've got a man living in my house

Don't get me wrong, I do know him. He's Isaac's daddy and my... ummm... my what? This is the problem I face you see. Because I'm not married to him, he's not my husband (although we live as man and wife). He can be described as many other things, but I find none of them fit quite right for the relationship we have. I cringe when describing him as my boyfriend as we seem a little old for that kind of thing... but then he's definitely not my manfriend as that just sounds weird. We're engaged so he should be 'my fiancee' but hes technically still married to someone else, and I'm not so keen on using 'my fiancee' as I seem unable to say it without sounding like Del Boy from Only Fools and Horses - "my feeeonsaaay". He's my co-habitee, but that's a bit functional and makes me feel like I'm involved in some kind of benefit fraud. He's my significant other - but as opposed to which other others, I'm not running some kind of man harem here. I usually call him "my partner", but when using that during introductions I always tend to feel the need to clarify that I'm not a lesbian, but by doing so I get a feeling that people are think "hmm the lady doth protest too much". Sometimes in a relaxed situation I use the phrase "other half" which is probably my favourite as that's what he feels like to me ... when I'm not with him I feel like I've lost something, so maybe its my other half that I've lost?  Whatever he is... he's alllll mine and I love him very much... even if all my yummy mummy pals that have never met him think he's a she ;-)