M cycles have been alternating 26 days one month then 29 days the next back to 26 then 29 again is that normal. how do i know when i'm ovulation ttc?

Yes : its normal with regards to ovulation you're fertile about five days before you ovulate. Ovulation usually occurs between 12 and 14 days before your period starts

Ovulation: Ovulation is often hard to predict. Most women do not have exactly spaced periods. Month to month variation that is consistently but equally different is a bit odd but it may be perfectly normal for you. Prediction of ovulation is not an exact science despite the hype and the products on the market. Try to have sex regularly in the week midcycle and you are more likely to become pregnant.

Ovulation: Ovulation is usually 2 weeks prior to menses meaning in a 26 day cycle around cycle day 12, and in a 29 day cycle around day 15. If you have sex around cycle day 12 to 16 (ever other day) you should conceive within 6 mos.

Normal variation: That is well within the normal range. You are ovulating on cycle day 12 to 15. Good luck.