I have been off bc for 4 months. I have ovulated between days 16-18 for the past three months. I am now on day 19 and have yet to ovulate. I had what I thought was EWCM on days 11, 12 and 15. I'm nervous that I am not ovulating. Any ideas why this might be happening?

PS---my cycles have been between 28-30 days. Last month is was only 24 days. I dont know if this could be the reason.