I Am On The Combined Pill However I Missed A

I am on the combined pill however i missed a pill on tuesday and took it on the wednesday just before i took wednesdays i then had diarrea on thursday which lasted until friday at 6pm just before fridays pill.. the diarrhea was severe to begin with up until thursday evening when there was not much to come out and then it was still constant but only little bits.. i took the plan b pill saturday however i am concerned about pregnancy