How long did it take for a positive to show?

I've taken 3 pregnancy tests so far and all have shown Negative. But I'm 18 days late😳. The excruciating cramps I have normally experience every month didn't show up. I feel good - no mood swings, no breast tenderness, no nausea....no period, lol. But really, wondering what is going on with my body. Going again today to purchase a different type of test - I've used 2 from Dollar Tree and 1 First Response (then I read their new  sticks aren't that reliable). 🤔