First day of period...

Hi, I'm new to all this so please bare with me :)

Me and my partner have been TTC for nearly 4 years and got no where, I have no clue what my cycle is as I dont know what to count as the first day of my period, this is because my periods are so irregular and some months it can be a brown goo, other times it can be bright red and extremely heavy..

So my question is, when should I start counting as the first day? When I spot the brown discharge, or from the first red day?

Thank you for taking the time out to read this, i really look forward to your replies xx