Help?

Sian
Im 17 DPO right now with no sign of AF whatsoever! Glow predicted it to be 3 days ago. I've been experiencing these symptoms:
​fatigued in the day
trouble getting to sleep at night
Nausea morning And late night 
Emotional
Back ache
Sore boobs/nipples
Runny nose
Metallic taste in mouth- like I've been sucking a key or something! 
Diarrhea (sorry! >.<)
​I took a test 4 days ago but got a BFN.
​Do you think I could be pregnant? Is it still to early to re test?
​Thankies :) xxx