My period was a day late last month, does it mean that i didn't ovulate last month? i think i ovulated early this month by 4 days.

Menstrual bleeding: Your menstrual cycle can vary somewhat each month and still be normal and you will ovulate each cycle. Some women will have some spotting for days after their cycle ends. I would monitor your cycles using an ovulation predictor kit for a while to find your normal pattern. You can talk to your doctor if you become concerned or can't confirm that you ovulated.