Cryptic pregnancy?

Latoya
Ok so I get my period every month when I'm supposed to, and every since 6dpo I've been having light cramping. I was supposed to start my period on the 18th but nothing, so I'm like 6 days late. I've been have pregnancy symptoms. Every home pregnancy test is negative and the blood test was negative. Does this seem like it could be a cryptic pregnancy? Has anyone ever had that?