12 days late..

Lauren
Hey all, I'm 12 days late for AF. I did a test at 5 days late but negative. I'm hesitant to test again because I don't want another negative. I've lost my appetite, my back is sore 24/7, I'm constantly tired, and feel sick every time I finish eating. I've been told you 'just know' when you're positive but I don't feel that, despite the symptoms and late period. 
Also got off my pill 3 months ago and have been told it can take months to regulate my period again so I keep thinking that's what's happening. 
Should I just test? Or keep waiting? X