4 days late but negative test..

Is it possible that I'm still too early for a positive? I hate to sound silly, because ive Ben pregnant before, but with my first I tested the day I missed my period and it was an instant positive. This time that I've missed I got a negative and now at 3 days late, I got another negative. 4th day with a no show aunt flow. So what the hell? I'm always regular, and I haven't been stressed, nor has my eating changed..