Had protected sex on the last day of my period, took plan b that night. now 7 days later, brown discharge. pregnant? on birth control, 3rd month.

Hard to tell...: Shouldn't be pregnant if taking birth control pills properly. If worried about pregnancy, a urine pregnancy test gives a reliable result if done correctly and read correctly, 3 weeks after sex or 1 week after missing a period.

Check preg test: Start with an over the counter pregnancy test. You can find out if you are pregnant or not in a few minutes. Plan b can cause some irregular bleeding. You said you had protected sex and are on birth control. Plan b is not needed when you are using condoms and taking birth control.

Time for a visit: For your peace of mind, it would be a good idea to visit your family doc or ob/gyn for a test.