6 days late

I usually get my period on time every month, but two days ago I noticed it hadnt started yet . Yesterday is when I started to panick and bought a test but it came back negative. Today I woke up and wiped and just a thin small string of red was there(literallylooked like a tiny red string). So I put a tampon in to prepare for my period but its been about 14 hours since the red string and it still hasnt started. Is this normal for some people . I know if Im that concerned I should take another test but im nervous that im taking the test early(test is from the dollar store).* I usually go by the app, ive had it for just about ten years and it hardly misses