help!!

I am 12 days late tomorrow will be 13 days for AF I've never been late before, my husband and I have been trying to conceive since May of last year, I've taken several pregnancies test and all have shown negative, my husband is making an appointment for us to get blood work and all done tomorrow, has anyone ever had this happen and been pregnant with just low hcg levels? I'm really just confused and would appreciate your honest opinions on whether I'm pregnant or not especially if anyone has any simaler stories