What Causes Milk Production During Sex Years After Stopping Breastfeeding?

i have breastfed my baby girl and stopped 8 years ago. Recently, i have a new partner in my life and i love him, when we have intercourse my breasts starts producing milk again, one of them is sweet, and the other is bitter. Why is that? can my bitter breast milk go sweet too? is it bad for my partner to taste of my milk?