Yes it is very possible. Untill your hormones go back to normal a pregnancy test can still read positive. It works using hormaone readings and it will take a bit of time to read regular-but a doctor can check you and that will be a positive answer to your questions.
Until all the hormones are washed from your body, you can still show positive on an OTC pregnancy test. The earlier you miscarry the sooner the test will become negative as there are fewer hormones in the body.
It is possible to have inconclusive test results, but not to test both positive and negative at the same time.
No it is not possible to test for salvia.
It is possiable to test positive if you where using k2.
Yes, it is possible for a person to test positive for the Elisa test but negative for the Western blot test for certain conditions.
yes
yes.
Anecdotally, yes, it is possible.
No
no
Even if you miscarry the test will show positive for a few weeks after. It takes time for the hormones to settle. If you suspect a miscarriage you have to see the doctor to make sure everything is gone so you don't get infections. When they do the ultrasound they will also confirm if it was one or not.
There is always a chance a pregnancy test can be wrong, and there is also a chance you may have misread the results of the pregnancy test. But assuming the test results were accurate, you need to see your doctor ASAP.