My advance clear blue opk only showed flashing smiley faces. it started on day 18 of my 24 day cycle. what's wrong? dr says my hormones are all normal

OPK: Once you surge, you will have a positive for a few days afterward. You also may have a short luteal phase. It might be of value to get a mid cycle pelvic US to get a follicle count and see if any appear mature (typically 15-22mm in size). You may want to change the time of day you test with OPK also. Some surge at night instead of morning.