Change in cycle how do I track?

[lilyborderterrier]

So 5th month of trying to conceive baby number 2. I usually have cycles of 31 or 33 days, but this month I started my bleeding on day 27 ( 4 days early ) i only bled for 1 day ( usually I bleed for 3) I hate stomach cramps and head ache as usual. ( I was thinking implantation bleeding but a test today was negative ) so do I calculate my ovulation dates from this months shorter cycle ( was it my body being cruel ?) or do I stick to my usual cycle of 31/33 days ?
I'm confused

You could have had an anovulatory cycle meaning you didn't ovulate. It's normal and does create a lighter period earlier. Unless you know how long your luteal phase is you can't really calculate when you ovulate. Your luteal phase can be anything from 12-16 days (normally, however people do have shorter ones and it can cause problems conceiving). You have two options, you just dtd every other day throughout your cycle, or you start using ovulation tests. Ovulation tests don't confirm ovulation but they can tell you your body is gearing up for it. You can use basel body temperature monitoring to confirm ovulation.