thanks for writing.
use induces menses within 10 days of stopping the tablet.
In your case since you did not menstruate the first possibility can be pregnancy. But your urine test is negative so it excludes pregnancy to great extent.
You need to get an ultrasound
to rule out other causes of delayed periods like ovarian cysts, polycystic ovarian disease
or any pelvic inflammatory disease
Ectopic pregnancy can also be one possibility.
So do get an ultrasound.