9 days late, BFN

Ok this is a crazy/weird question but...my last "period" was on time but it was super dark & light flow and lasted only about 3 days. This cycle was supposed to start on the 3rd of this month...still hasn't showed. I'm always regular, nothing has changed, no extra stress or anything. All the at home tests I've been taking are negative. Has this happened to anyone? I'm thinking a blood test should be next. Any advice!!