Does the plan b pill also cause breast pain and altered vaginal discharge coming out?

Possible: Plan b is a progesterone. Progesterones can cause breast pain (especially nipple pain or irritation). Progesterones also cause a thickening of cervical mucous which can affect the nature of your vaginal discharge.

Maybe: Typically it does not cause breast pain but it can bring on your period early or cause thickening of the cervical mucous. It doesn't ever cause any kind of infection or a change in your vaginal discharge for long. If you needed Plan B once, go get on better birth control.