When should I test?

Hey ya'll. I've never been good at knowing when to test because I've always "just known" when I was pregnant. Since my very first period I've always been EXTREMELY irregular. (They tried to fix it with BC with no avail and they ran test, I'm just irregular and that's all.) Glow says I was suppose to start yesterday, but nothing. I've taken a few cheapo tests over the last week cuz I feel like there's something going on (maybe I'm just too hopeful) but they aren't early detection. So my question is, when should I test if I never know when I'm truly "late"?