Wow... I could say the exact same thing right now, except my husband had a vascetomy about 3 years ago. So we KNOW there's hardly a chance of me being pregnant. But yet I've missed my period in april and also have two negative pregnancy tests.
In my case I'm probably late just due to pure stress. Too many things going on (jury duty, fix it ticket, kids' conference with school, money issues).
I called the doctor office and I was told that I could come in and they'd draw some blood to test for pregnancy that way, but for me it probably would still come out negative. (home tests could always pikc up a pregnancy a couple days before i missed a period the two times we expected one.) Otherwise its just a matter of waiting. A nurse friend suggested that I go in and get a pap smear, but that's something I'll be doing in the next month or so anyways - since its been a year since my last one.
Wishing you the best and hope that helps
D.