It is possible that you have an ovarian cyst and that is what is causing your period to be late :) I hope this helps. There are a lot of other things that can cause your period to be late. If you want to be extra sure about the pregnancy thing go to your doctor and have a blood test done and those results will be way more definitive than a urine test.
It is so ironic to read your story. Get this, my perion was supposed to come on March 9th as well. Didnt think much of it but I went to the hospital Wednesday because I thought something was wrong with my kidneys. So they take my urine and come back 15min later and tell me I have a UTI and I am PREGNANT!!!! I was so upset, but the crazy part is I have been having piercing pains on the lower right side of my stomach and they hurt and come every 3-5 min. I was thinking I may have an Etopic pregnancy myself. With this being my 3rd pregnancy I do know that I have never felt these pains in either one of my past pregnancies!!!