Clear blue advance ppl

Ok so I've been using the clear blue easy ovulation prediction kit. This is my 7 month using this system and no luck yet :/.  However I have noticed something strange. I usually test and get that flashy smiley face which means lh surfer is high and ovulation is right around the corner. When I get my first smiley face I usually stop bc O is supposed to come 3 days during the next couple of days. However I notice I was getting AF later than when I thought I was ovulating (bc of clear blue) and I wasn't BDing  when I was supposed to. So here is my problem now. I have taken my opk and got a surge on Sunday which was the flash smiley face which was CD 15 and I am still getting them on CD 18  which is my 4th day of flashy smiley face. Does this mean I'm still waiting to O?? Is it possible to LH surge more than 2 days before ovulation? Any thoughts or insight!??? This could have been the problem for the past 9 months of TTC! I thought I was Ovulatikng when I actually was only surging! bbt. Was still increasing today too. Girls help me out!!  Ps goin to Fert doc on April 9