False negative?

I recently had a miscarriage in March and had one successful period 6 weeks later. I'm now almost 2 weeks late on my period and I have a small feeling I may be pregnant again. I'm nauseous every morning to the point where I cannot even eat anything. I've taken two clear blue digital pregnancy tests and they are both negative. Has this happened to anyone that has turned out to be pregnant? Or can my body just be trying to get back to normal from the miscarriage. Would love some advice!