HELP PLEASE

Gussielee • gave birth to a beautiful baby boy April 28 2015
This app say I'm due for AF on the 24 and test for pregnancy in 7 days Glow said AF suppose to be here today and it's not and took a test BFN CAN It still be to early to detect the HCG are should I actually wait until the end of the month when my cycle is really due that's when I normally get my cycle towards 23- and up ​the