I am 4 days late and my boobs seem bigger and todai I started with brown discharge.. I don't know what is happening x

It is possible that you are just running a little late, a menstrual schedule is not always set in stone as to when it will or will not happen. Brown discharge is also fairly common as the beginning or at the end of a cycle.

Breast may swell before or during a cycle, so there should be no reason to worry; they may also get sensitive to touch.

I suggest you wait, and if it is more than 10 days late, go and talk to a doctor for a professional opinion