How do you know when to test?

Ok so I am 3 days late and my period is never late. I took a hpt today it was negative. It was one of the $.88 ones from Walmart do those not always work as good? Or is it normal to not get a positive test this soon? My other 2 pregnancies I didn't test right away cause I was in denial that I was pregnant but I think I know the signs well enough by now but I'm not getting a positive. Maybe I'm just making up signs in my head but then a late period doesn't make since. Can anyone help?