your cycle starts the day you started your period.
if you normally have irregular periods it can be hard to know when you will ovulate.
because normally you ovulate about 9-15 days BEFORE your next cycle starts.
the beginning half can be any number of days. but textbook 'normal' is also around 9-15 days. Like you always hear that it is 14 days. that is based off a cycle that is only 28 days. 28 days give or take a few. but it sounds like you arent in the 'norm'. which many of us aren't.
try and pay closer attention to any signs your body is putting out, like your cervical mucous. it usually gets creamy before ovulation and then clear and stringy with ovulation. those are the best times to baby dance for trying to conceive. you also might feel mittlescheitz (sp?) ovulation pain. slight twinges or little stabs near an ovary, signaling an egg has 'dropped'.
i hope this helps good luck
at 4:52 PM on Aug. 3, 2009