First time oral sex??

So I'm nervous af! I've never had anyone go down on me anddddd my partner wants to...now I've previously had a issue with my taste being kind of sour in my opinion though? Like I've had sex then went down on a guy before and it tasted bitter so I've always been self conscious i guess you can say about someone doing it to me. Soooooo..idk? Idk what to do or how to go about it but I don't want it to be weird or embarrassing. Help help help! Suggestions?