My partner won't go down on me...

We're married and he had a bad experience the first time he went down on a girl. Long story short the girl was on her period and didn't tell him and now I can't get him to ever go down on me no matter how clean I am. I know once he's comfortable doing it we won't have a problem but I don't want to make him do something he's not ready to do. We tried once when we were dating and that was well over a year and a half ago.. Any tips?