So my boyfriend thinks that I'm pregnant

Arisha • In a relationship truly blessed with an amazing family. A daughter to two fab parents a sister to 3 sisters& 2 brothers
My boyfriend thinks that I'm pregnant when I'm not.
So basically I've been sick for the past week or so and I've got a headache and he thinks that there's some good news coming his way and I've taken the pregnancy test and I've been to the doctors and they said there's no signs of me being pregnant
But he just won't believe me. 
What should I do? Have you got any advice for me?