Hello, and I hope I can help you today.
Plan B one step is extremely effective in preventing
pregnancy when taken within 72 hours after intercourse.
The way Plan B works is by creating a hormone surge in your body that that both thickens your cervical mucus and prevents ovulation in the 72 hours while the sperm could still be viable in your system.
The drop in hormones that occurs when Plan B wears off commonly causes bleeding or spotting anywhere between a few hours to five days after taking it. This is actually most likely a sign that the Plan B is working. The other possibility is that if your period is due soon, the Plan B may be just making it come early.
So in summary, it is common to have a small amount of bleeding (which when it is like can appear as brown discharge) after taking Plan B. There is nothing to worry about, and in the scenario that you mentioned, especially because your partner did not ejaculate inside you, your chance of pregnancy is extraordinarily low.
I hope I was able to adequately answer your question today, and that this information was reassuring.
Best wishes,
Dr. Brown