Help please

Desiree • Sun, May 22

My period is way late was supposed to start the 11th but still no bfp I've taken at least 4 tests throughout this time frame and all are very faint(just barley able to see a line) even the one I took on the 21st I don't know what could be going on. Shouldn't the line be getting darker? I added the last three test i took(second one was the strip inside a digital)