when can I test

I would be 3 weeks 3 days today, when can I take a test? I was reading you can take one 7 days after ovulation or should I wait till I'm due for Aunt Flo which is in 6 days ! I have had mild cramping, fatigue, and constant headaches I'm trying not to get my hopes up as it's our first moth ttc but gosh I'm excited !