When can I take another test?

Krista

Hi ladies! My husband and I have been TTC for 2 years and this is the first time that I have been significantly late. I took a test on Sunday night (I was 4 days late then) and it was negative. I am now on day 6 of no period, but I am not sure if I should take another a test or wait. Also, why would a test be negative if I am 4 days late? This would also be my first pregnancy.