2-3 days before the start of my period, I normally have a brown discharge. It ends up being a black discharge. I have a 28 day cycle and normally calculate ovulation from day 13-15. Am I calculating my ovulation correctly? Do I include the 2-3 days brownish discharge as day 1 or do I start calculating from the time my period have the normal reddish colour. My period started on 1 March 2004. But I had the brownish discharge 2 days prior. I presently cramps.

Thank you