Positive home test, negative Obgyn test

Tina
I've had a positive digital test, two clear blue positive tests and a ept positive test. I had my appointment this morning with my Obgyn to get a confirmation test and it was negative. They said it might just be too early to detect their test since I'm only 4 weeks. They want me to retest in 3 weeks. Has this happened to anyone else that had a normal pregnancy?