my husband and are trying to get pregnant, i have been keeping track of my cycle length in order to use ovulation calculators, my cycle went 26 days, then 24 days, and most recently i went 30 days, got my hopes up and on what would have been the 31st day i started lightly bleeding, it seems possibly lighter than my normal period ,but not as light as what is described as implantion bleeding in my opinion. if i am not pregnant how can i use these cycles to help calculate my ovulation when they vary so much? i have had no significant changes in my life over these changes that i can pin point, and no physical changes either.