Why do I taste sour??

Grace

So I asked my boyfriend what I tasted like when he gives me head cause I’ve tasted myself before and it was almost sour. He said I tasted super sour/tangy and that it’s actually been more intense recently. I wash myself with an unscented soap and never get any inside, I also drink lots of water, and wear breathable underwear. Why do I taste so sour???? What can I do to help? Is this normal?