Irregular periods.. how do you track ovulation?

my husband and i have been ttc our first for about 8-9 months now. i have irregular periods so much as i can go a good 6 weeks with out a period at all. i went to the dr and they did a sonogram to check my ovaries and they let me know that there was nothing unusual about them... so its kinda unknown why all of a sudden i got irregular. nothing has changed in my weight or diet.. so i dont know!! but it makes it so hard while ttc. so i was wondering what you do if you are irregular as far as pinpointing your ovulation days. someone told me to go by CM, so i did and i THINK its possible i ovulated on the 29th. my LMP was on the 13th. my husband and i BD on the 25, 27, 29, and 31. so now i am playing the waiting game. :( its hard and i dont want to be let down again. any advice would be VERY much appreciated and please send baby dust and prayers my way. thank you!