Missing period after ending birth control

Patient: I stopped taking birth control around March/April. The day after I stopped it, I had unprotected sex but the next day took Plan B. Maybe a week or two after that I had my period for 2 weeks. I haven’t gotten my period since then and took two pregnancy tests about 2 weeks ago which both read negative. What could be wrong? Could I still be pregnant? Or am I working myself up over nothing?

Symptoms: Missing period