^Helpful tips here, a blood test is more relevant then going for a urine test, even though u should do it in the morning, because your hormones are strong enough. Plus, I got the same brown reaction, but this was the end of my period. Sometimes I do get a liquid smooth and sticky reaction.
wait out another few days or weeks, then go for the blood test, the results will tell u honestly if you are positiver/negative.
Are you sure the first test you got was positive? It's not common to have a positive and then 3 negative right after. I would go get a blood test done to confirm whether you are or not. Many things, not just pregnancy can cause the symptoms you describe.
Miri,
My advice for you would be to seek advice from your doctor. Sickness, and tenderness in the breast can sometimes be an indicator of pregnancy, but I would test again.
In fact, I would go to the doctor for a test, rather than buying your own home kit considering you have already recieved mixed results.
As for the discharge and diarrhea, mention this to your doctor as it may be a key part of his diagnosis.
All the best