How is it, I took 2 Answer Pregnancy Tests Yesterday, 2 First Response today & got positives only yesterday!?

My husband and I are TTC. I took the tests yesterday after experincing a very short & light "period". This "period" lasted 1-2 days and was very light & didn't cause me cramps or anything. So yesterday morning I got 2 positive test results with the Answer. Retested this morning with First Response to confirm before making a doctor's appointment and I get 2 negatives this morning. Both tests were used with first morning urine. I have been naseous, tender , heartburn, and after experincing the strange "period" I did I would consider myself to have pregnancy symptoms. Am I pregnant or not? I really appreciate anyone's opinion. Thanks!