Help! Ttc with really irregular periods

So I had my ectopic and tube removed 1st feb. Since then I have kept track of all my periods and they are all irregular. Between 19 and 31 days. I also haven’t been able to get a positive ovulation test since ectopic, just faint lines. Doctor has blood tested me and has said I am ovulating but since I have no idea when that is, i can’t pinpoint my fertile time to conceive. I have to go back after Xmas. What can they do for me? Can they give u anything to make periods regular?