Had marina removed begin of sept.sept-oct 28 day cycle.oct-nov 32 cycle.believe i had a failed implantation. how can i work out when i ovulate please?

Use an OPK kit: Did you have a + pregnancy test then negative? Now your cycles are back after the Mirena (levonorgestrel) you can use an ovulation predictor kit (opk) - test between 10 am and noon, starting on day 10 of your cycle. The first morning urine is not accurate. Try the ovuquick brand (available online) if a drugstore test doesn't work for you. The day of a positive test and the next 2 days are your most fertile days.