Obstetrician Leonie says: If you have an irregular cycle, it is more difficult to know when you are at your most fertile.
Women with polycystic ovaries ovulate less frequently than other women, and in some cycles may not ovulate at all. If you do ovulate, this will have happened 14 days before the first day of your full period.
If you have a long but pretty regular cycle, it is more likely that you do ovulate and also possible to work out a likely fertile period.
From your description, your cycle is 33 to 37 days. This means that ovulation occurs on day 19 to 23 each month. As sperm can live for about two days before ovulation and the egg lives for about three days after ovulation, your fertile period is within the timeframe of day 17 to 26 each month.
This is a longer timeframe than for a regular cycle (where the peak fertile period is day 12-17). An ovulation prediction kit used during this time would allow you to pinpoint the time of ovulation more accurately.
The bleeding that you have a week before your true menstruation is not your period, but it is unlikely to be the small bleed that can occur at the time of ovulation.
If this irregular bleeding continues, you should see your doctor as investigation, such as an ultrasound of your uterus (womb) should be arranged.