could be a lot of things stress, weight gain or you could be pregnant and you just don't have enough HCG yet. I would go get a blood test two weeks late is a lot to not know.
I'm going through sort of the same thing right now. But I am almost 4 wks late and no bleeding anything since April 10th. I've taken 2 HPT's and had a urine test done at the dr and all negative. They told me to wait until my next scheduled period and if I don't get that to come in. Don't know what they plan on doing, but I hate waiting! I know my body and something isn't right!
Have a blood test done, it's your best bet for now. Also, are you on a low dose birth control pill by chance? I am and the dr told me that sometimes a woman can miss a period on such a low dose.