Chemical pregnancy?

I had a faint line on my first response early result test a few days ago on Wednesday (6 days before AF) and when I took another one recently, the line is even fainter than before. It’s almost barely there now. I also took 2 clear blue tests (it had pink dye) and they were negative. This morning with FMU, I took a clear blue digital test (it says you can take it 5 days early on the box) and it said “not pregnant”. AF is due in 3 days. Not sure what is going on. I’ve been pregnant before a few months ago and I got dark lines days before AF was due. I’m talking about I saw lines pretty well 7 days before. On the 5th day back then, the lines were so dark. It was obvious I was pregnant. Now 3 days away from AF, all of a sudden, it’s like nothing is hardly there. Why would the lines become lighter as if they’re almost not even there now? Has anyone experienced this and what was your outcome?