late period but negative tests!

I haven't had a period since September 23-28. I've took 3 pregnancy tests since and all negative, not even the faintest line. I stopped taking my bcp in August and I'm new to everything about a full period. I've been on the arm implant since I was 13 and had them removed every 3 years but with the implant i never bled.. I never really had regular periods. Just light blood for a couple days each month. I've been on bcp since March of 2017. (rough estimate)so not even a year. someone help?