BFN after possible BFP... confused ???

My period is supposed to start tomorrow. This morning, I took my first test of this cycle and I thought I got my BFP! It was a cheap test but not expired so I thought I could trust it to be accurate. While I was at work, I asked my husband if he’d pick up some First Response tests so I could confirm tomorrow. This afternoon I got home from work and was too excited to wait to test again (since I’m addicted to looking for that second pink line!) so I opened up the First Response test only to get a BFN!

Now I’m just confused! Could a cheapie test be more sensitive than the FR? Is it because hCG levels decrease after the FMU? Was my test this AM not actually positive?! Help, please???!?

Here is the test from this morning, taken at 2 minutes. I didn’t even bother taking a picture of the FR test from this afternoon because there really wasn’t a second line at all.