Very confused someone please help me

I am 5 days late for my cycle I have taken 3 diff tests, two first response rapid result tests and a dollar store test all were negative.i haven't had any PMS symptoms I have been having cramping for over 2 weeks now, lower back pain and terrible fatigue. I have 2 children already and when I tested positive with them it was within 4days after my missed period. Someone please help shed some light on my situation