Need some insight

Kayla
Okay this might be TMI for some so fair warning.
My period is always like clockwork starting heavily however this month it was a couple days late and it was almost like an extremely slow/light start over those 2 days (I'm talking extremely light, nothing when wiped but there would be a teensy bit of blood if I inserted my finger). Then had what would be a "normal" period for me for 4 days (a little short though my periods are usually 5-6 days) now I'm having 2 days of it being extremely slow/light again waiting for it to finish. So my question is when do you think I should put my period start and end date? I've never had anything like this before so I'm a little confused if I should count those days or not but want to get the most accurate dates for my fertile window so I'm testing at the right time. Thank you in advance