BFP to BFN with no period???

Jo
Why did I go from vvvvfl BFP to obvious BFP (was darker when I first took the test) to now negative for 4 days in a row? I haven't gotten a period in 90 days (recently stopped BC) and no sign of one now? I know of chemical pregnancy but I have no symptoms of a period coming but my breasts/nipped are so sore