Pregnancy tests with differing results? Could I be pregnant?

I took a clear blue digital two mornings ago as soon as I got up and it clearly read pregnant. I took a clear blue regular test as soon as I got up yesterday morning (where it makes a plus sign if pregnant) and it clearly was negative. Today I took another clear blue digital test as soon as I got up this morning and it said "not pregnant". I am currently five days late on my period. My last period was June 27- 5. I had relatively heavy dark brown spotting not long after. I have a doctors appointment coming up, but if really like to know for sure before then. I know chemical pregnancies are a thing, but wouldn't I be bleeding if I had one by now? Or if my spotting was chemical pregnancy bleeding, why would I still have gotten my period last month? Has anyone had these issues before? Is the digital test more sensitive to the HCG hormone? What are your experiences with the tests? Please help. I'm desperate! Thank you!