Talk to your mother. If she's no help, talk to your grandparents. You have a right to basic information, particularly about the possibility of genetic diseases.
And, recognize that if you've been told absolutely nothing for all these years, the chances are really, really good that what you're going to be told is not going to be a pleasant romantic fantasy but, rather, that the guy's in jail, dead or was married when you were born, or something else, equally not so nice. Not to throw a huge wet blanket over you but if you are fantasizing about a beautiful home and family life, well, there are often damned good reasons why the kids are told nada about the Dad.