Further gone??

Has anyone ever been dated by their doctor then the scan completely change it? Like by weeks rather than just days?? As silly as it sounds I'm wondering as I stopped my pill in August 2015 and since then my cycles had been between 34 to 37 days long and my periods have been 5 full days exactly each time. Until my last period in Feb. My cycle was only 29 days and period only lasted 3.5 days... anyone think this could have actually been implantation bleeding instead of an actual period?? Anyone had similar experience???