positive then negative ???

so I took a test yesterday morning and it came out positive!! I was so excited and of course just wanting to double check.. I took another later that afternoon and it came out negative .. well I was upset but I thought it was just because I should have taken it the next morning well the day went on and then the next morning came, I wake up anxious to take the test .. so I did. but.. once again a negative ?? I don't understand . 😔