missed period 13 days, been trying and off the pill for four months and trying.

Hello, I've been off the pill for four months now and my husband and I are trying. Since off the pill my periods have been consistent. I'm 13 days late and taken numerous test that day negative... should I assume that the test is correct. I am new to this and am unsure what to do. I've never been pregnant before so I'm unsure if I'm just being crazy or what.