I need your help girls please...

Ok so starting from last year I had a MC in June, both before and until this month my period has been like clockwork! Never late - it could nearly be timed! But this month it never came and I'm now 7 days late, BUT I've done tests and all negative :-( what is wrong? When I found out I was pregnant last year I was 12 days late before I tested and it was positive. So am I testing slightly early?  I am experiencing some symptoms, like stabbing pains in my boobs, slight nausea and headaches and lower back pain! :-(