8 days late.

AF 8 days late, I have taken quite a few tests, not in the last 3 days because the rest have been all negative. My friend whom is pregnant at the moment thinks I need to go get a blood test done. My symptoms have been kind of the usual PMS symptoms except my nipples are non stop perky. I feel like I have to wear a sweater EVERYWHERE I GO! As well as just soooo thirsty. Haven't been very crampy. My last period was roughly beginning of February. Just hoping for some more advice! I am leaning toward just it being a late period.