I am trying to conceive married 18 months ago my egg size is 14mm what is the reason of not conceiving ?

Can't say: The follicle size changes as the egg develops so knowing the size at any point in time doesn't necessarily say anything about fertility.There r many possible causes for ur trouble conceiving including low sperm count,lack of ovulation,poor quality cervical mucus, blocked tubes,allegy to his sperm,etc.A full workup is necessary to know for sure and hopefully be able to fix it.It can b a combination