When to know what day cycle one is

I don’t know if this happens to anyone else but I normally spot for a few days before period starts. I normally don’t count as I’ve never TTC before. But now that we are. I’m trying to be more aware of how the cycle works. I’m having a hard time figuring our when I should say my period is starting so I know when fertile window is. This month I have spotted for 5 days with pink brown and one day on day three with a few wipes of bright red. But only wiping. Not enough to be on pad or even in toilet. Today I had enough to be pad and in toilet. Would today be considered day one or maybe the day I first saw bright red?