Cd1.. Confusing cycle!?

So this has been my first irregular period since we started ttc 3 months ago. I had a terrible cold and flu virus during my predicted fertile window and I think I either ovulated later or didn't at all this month (not to mention it limited our bding) My period was supposed to start Thursday of last week- nothing, Friday I had light spotting, Saturday nothing, and Sunday and Monday red blood then stopped. (usually my periods are five days). My question is- what would you consider the first day of the cycle? I'm confused that it skipped a day (Saturday) because I usually start period flow a day after spotting starts. Thanks!