Positive then negative?

I experienced what I thought was implantation bleeding on 10/13. It was extremely light and light pink spotting about a week after we had unprotected sex.. fast forward to yesterday morning I took the test below and I assumed that it was a positive test.. I took two more yesterday and they were both also faint positives. Then I woke up this morning expecting for the line to be darker and the test was negative. I took two more tests and they were negative as well.. all the same brand (FR) and all taken within the time frame. Has this happened to anyone?? I went to the Dr today to get a blood test but the wait is killing me since I won’t get results back until next week. I’m just so confused!