Period is late but the two pregnancy tests I have taken have shown to be negative?

My period is approx. 2 months late but the two pregnancy tests I have taken have shown to be negative and I have been free of the implant for 5 months.
Other symptoms include nausea and headaches but this has only been relevant for the past week or so.

Age: 21
Female
Medications: Sertraline and Propranolol

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