hello friends.....so i last had my periods in march 18th ...April i di...

hello friends.....so i last had my periods in march 18th ...April i didn't receive my periods tested for pregnancy and it turned out negative....may came and still no periods and the test this tike came positive so i expected my pregnancy to be 11 weeks 4days today but i went for an ultrasound and it turned out to be 6weeks 6days am confused