Hi have you tried ovulation kits just to make sure you are ovulating? Or tried taking your temp? If not it would be a good idea so you know if you are ovulating regardless of having irregular periods.
If you go to msn.Com and click on family they have where you put in dates of period and it will give you your most fertile time!!
I recently had a miscarriage and just past my ovulation time we don't know if i'm pregnant yet~ but I have irregular periods so i'm always tracking.We have been trying for l~o~n~g time.
Hope this helps