after removing Implanon it will take 3 to 6 months for regularization of cycles.
that may be reason for your anovulation
because of hormonal changes induced by hormonal contraceptives pap smear
can come abnormal sometimes.
you better wait for 1 week after the date of missed period and repeat the test as some urine pregnancy
test kits are less sensitive.
or you can go for blood test
for pregnancy which can be done now.