I've been having swollen tender breasts for the past two weeks and I took a pregnancy test 5 days before my periods and the result were negative, now I'm having some whitish discharge a few days before my periods... can u tell me what is going on??

Very common to notice white discharge before a period is due. As long as there is nothing else going on, itching for example, it is likely perfectly fine.

Since it appears you suspect possible pregnancy, see what happens when your period is due and test again if need be.
In early pregnancy there can be more abundant discharge as well.

What cause vagina to itch on the inside