Um, breast milk? Yes, as awkward as it might be, milk can spray out of your breasts when you're having sex. This is totally normal! If you are breastfeeding, you might squirt milk when you orgasm.
If this makes you uncomfortable, you can leave on your nursing bra or put a towel over your chest. You can also try breastfeeding or pumping before sex, but other than that there really isn’t a whole lot you can do about it.