tasting good down there?

so a few relationships i've been in guys have offered to give me head but i'm nervous because i don't know how i'll take down there to them. personally i have tasted down there before just to see if it'll be ok to them and it was kind of sour and then another time it was really sour and idk if this is ok and it makes me self conscious. any info on what's normal or how i can improve the taste?