Positive test, but doctor's test was negative

A
Hi everyone, 
So I'm about 12 dpo, period was due yesterday and didn't appear (still worried it might show up); I decided to take a clear blue test (digital) I took two of them and both came positive (1-2 weeks). Then I went to the doctor first thing this morning and the test was negative. 
I am so confused, and really disheartened. I'm getting on going cramps so I feel like maybe I am going to get my period despite these positive tests, maybe the doctor is right and I'm not pregnant? Has anyone gone through this?

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