Need HELP. Major tmi ahead.

When my man fingers me before we have sex he likes me to lick and clean his fingers off with my mouth and tongue. Therefore I know how my discharge tastes and it's normal, doesn't taste bad or anything at all. Now here's where I need help..... last night we had sex, he pulled it out of me before he came and told me to finish him off orally. And I did. However, my vaginal discharge taste changed. It was sour and absolutely horrific to taste. It wasn't like my normal discharge before sex and it had a different consistency to it. Does anyone know what this is????? Or why this is? Please help me.