4 days late and negative pregnancy test.

Stacey
Hello ladies, I could use some advice. My DH and I have been trying for a year and a half to start a family, so far no luck. This month however my period is 4days late and I never miss a period. I'm like clockwork. So how long should I wait before testing again, or contacting my doctor? 
Thanks in advance ladies.
Good luck to everyone out there. ☺️