An invalid test?

Yesterday, I posted a picture of my test, and it definitely had a faint line. You could see it without a doubt tweaked. Today, I took another test, the same brand and even at the same time as yesterday. Completely. Totally. Negative. I am so confused and upset, I don't know what to do now. Is it really worth going to get a blood test? Wait for AF in 5 days? Has this happened to anyone else? These are the Assured brand tests from Dollar Tree. Here are the tests from yesterday. I took one right at 1:45pm, and another 30 minutes after because I couldn't believe there was a line. Both had lines! What the heck is going on! Can you really get a positive one day and negative the next?