I have just experienced 3 positive OPKs 3 nights in a row (Sat, Sun and Mon night). Difficult to tell when the line was at its darkest as all 3 were identical to the control line as far as my eyes could tell. Could it be that I caught the surge at the very beginning and then again at the very end? Has anyone else experienced 3 positives over this time period? Can the surge last that long?