I have a 33-34 day cycle and this app and ovulation calculators say my fertile window was from 29th dec - 3rd Jan. We have bd'd 30th, 31st and today but I've taken digital opks every day twice a day over this time and they have all been negative so I feel I have missed my window :'( now have to wait another month :'(. Strangely I have ewcm and ovulation pain so not sure why all my opks are negative xxx