I am three days late on my period. i took the plan b pill about two weeks ago. took a pregnancy test two days ago, negative. could i still be pregnant?

Yes: Obviously you were very concerned about the possibility of being pregnant since you took plan b. Emergency contraception is not 100% effective, so it is certainly possible to be pregnant. A negative pregnancy test is reassuring but that is also not 100% accurate either way, especially early. Irregular periods can be from pregnancy, or other causes, so if worry continues, be seen and checked out.

Possibly: Being late could be due to the Plan B. If you have missed period by seven days, would take home pregnancy test again.