On my latest ultrasound last march 22-my first menstrual day is march 1, my left ovary has follicles & a cystic structure that measures 14.4mm; does that mean that my follicle size is too small for conceiving?

Follicle size of 14.4 mm may be at a pre-ovulatory stage, so obtain a ovulation test (most pharmacies carry them) and test daily for the next week. If the test (measuring LH ) is positive, pregnancy is possible (given other fertility factors are normal: sperm count, tubes patent, etc.) . If no positive on LH test (ovulation), see a fertility physician to evaluate status.