I used a cheap test 5 days after my missed period…it took me that long because this pregnancy completely took me by surprise and I felt like I was getting ready to start any minute for the entire week my period was supposed to come.
A HPT is most effective taken the day of or the day after a missed period. Even those early tests that claim 99% effectiveness only claim that high of effectiveness if taken the day of or the day after.
You can take one about 5 days before your missed period, but it is easy to get a false negative by taking it that early…and get an expensive one if you’re doing it that early, one that measures a small amount of the hcg hormone.
Good luck!