Conflicting tests?

I got a bfp at 4 weeks 3 days. I tested on three different types of tests, including the ClearBlue brand. All of them came back positive.

I had my first prenatal visit yesterday at 5 weeks 4 days and my urine test came back negative and blood hcg was at 5.1.

The doctor acted like I made up the positive home tests, but I started bleeding and cramping heavily last night and today and have passed a lot of clots and some tissue.

Does anyone have any idea what happened or had something similar happen to them? I’m so confused.