I'm getting scared am I pregnant or not

It's been 56 days since my last period. I've had three home pregnancy test all negative n one blood test two weeks ago it was negative also. I'm so confused because I've never missed a period before n if I'm not pregnant then what is it then. Or could my hcg levels are just to low to detect if I'm pregnant or not.. Someone please help if any one knows anything I'm freaking out really bad.