Help...Positive then negative then positive.

So last week at 9 dpo I got a positive first response pregnancy test. I went for bloodwork that day and it came back negative. So later that day I took the last 2 tests that were in the pack. All positive. I also took my cheap test strips which were all negative. So thinking maybe I got a defective pack I went and bought more and took it the next morning. It was negative. Today I am due for my period and for some strange reason I felt like I needed to test. I used my cheap test strip and got a positive. Went for bloodwork and now I wait. So i guess my question is...WHAT THE HECK IS GOING ON? How do i go from positive urine to negative blood to another positive urine test? I'm beyond frustrated at this point.