Pregnant or what???????????

Had on May 6th and had period on may 9th. we did use a condom and it seemed ok.. However on may 9th i started back on the pill and had again protected on may 11th and got plan b... I don't know why but am really tired, could it be because im back on the pill?? i also took plan b on the 11th within 12 hours.. i am so scared now.. wld i be having symptoms so soon???? I have done a test and its negative..