First day of period

What day do you consider the first day of your period?...I have brown discharge that normally turns into bright red blood a few days after and on that day I have the worst ever cramps (usually) however this cycle was different I had brown...the bright red once when I wiped...then brown again..and then BAM the day came where it was bright red and cramps...so I don't know what day is the first day of my period? Help :\