Hi there!
Well, there is always the possibility that you are pregnant. Don’t get stressed out about it, but do start acting as if you are pregnant (don’t smoke, drink or whatever).
Get another pregnancy test and take it first thing in the morning (when your urine is more concentrated).
For some reason pregnancy tests don’t work well for some people. You might want to go get a blood test. (or just get a slightly better quality pregnancy test!)
Make sure to let us know what happens, ok?
Good luck hun!
Hugs!