Negative at the doctor’s

I had a miscarriage April 11th. Since then, they tracked my blood until the hormone completely left my system as well as have gotten negative tests. Three days ago, I got a positive on a Walmart cheapie. I hadn’t tested again since then. I just came to the doctor’s office to confirm my pregnancy and they told me it was negative . I just don’t understand how this is possible. I had already shared the news with immediate family because I just wanted some positivity going forward. Is it possible I am still pregnant and their test didn’t pick it up?

The one positive test was not super faint, but also wasn’t dark.

They are going to run blood tests to make sure. I’m just a wreck right now.