Confusing AF?

I started what I thought was AF Monday(2 days early 14 DPO) it only lasted about a day and I half but was kind of heavy and bright red for just a little bit Monday and then lighter for the rest of the day and Tuesday... my cycles are always between 5-7 days. Is it normal to get a very short period? I wasn’t overly stressed this month at all but I did take Letrozole for the first time. I’m suppose to start letrozole on CD 3 this month (which would be today) but I’m nervous that this could have been something other than my actual AF..