Positive OPK but small follicles!

Hi ladies! I went for an ultrasound yesterday and my LH was 6.9 and biggest follicle was 13mm. The Dr told me to go back for another ultrasound in 3 days!! Today I took a digital clear blue opk and it shows Fertil day! Am I ovulatiing? If so, is gonna be too late to go back for an ultrasound on Sunday ? Am I ovulating immature eggs!? I'm so frustrated and tired of guessing everything!