How old are you? The younger or older you are, the more likely you can have irregular periods. Do you normally have regular periods?
Did you follow the directions in the pregnancy test box? How soon after your missed period did it say to test? Five days may be too soon for the test you used. They vary. I would check the directions and re-test when it says it's most accurate.
If you aren't pregnant, go to your doctor and get some birth control so you don't have to scare yourself like this again. Okay?