I use the term 'husband'. Since we will be crossing the 27 year anniversary of the start of it all in a couple of weeks, 'boyfriend' would just seem strange ... "you mean that after 27 years, you still haven't gotten past dating?" We were actually business partners for 3 years, when we decided to drop out and open a bookstore, but 'partner' is too sterile and misleading.
If we were an opposite sex couple, the state of Texas would absolutely insist that we are married under common law, so I see no reason not to use the terms accorded to a person who would commonly be recognized as a party of a civil marriage, even if the state refuses to legally recognize it. And, since there are two males and no females in the relationship, we each can be properly referred to as the other's husband.