You could call him your 'partner', which is the term a lot of people use in the UK. A more informal phrase which people use here is 'my other half'. Or, If you want to call him your husband, that's not a problem. It's up to you.

You could say "long-time boyfriend." Husband wouldn't technically be correct, but if you want to call him that, marriage is just a sheet of paper after all. :)

In Britain it is very common for unmarried couples to live together and have families, and in this respect they are regarded no differently from 'married couples', and legally (under common law) they are known as being husband or wife, hence they just use 'husband' or 'wife' Others prefer to use the term 'partner' when referring to their live-in boyfriend or girlfriend.

In the U.S., you can say "My Significant Other" or "live in boyfriend". As you mentioned, using "husband" tends to legally mean you are actually married. However, I understand other cultures don't require this.

If you view him in this way, feel free to say 'husband'. Your relationship is not less than that of a couple who have signed a piece of paper. Also, the exact details of your relationship are nobody's business but yours. Of course, for legal or official purposes, you should not say 'husband'. But in social situations, go ahead.