Told no...but could I be?

It's been awhile since I posted an entry. I just have been down and depressed that I have not gotten pregnant yet, and the past year has been so stressful with getting a new job, and having family issues. But I am back now. My back was botherin me really bad on June 8th, I went to the ER, and before they did Xrays I had a PT taken (urine) and it was negative. So I had the Xrays and we on some drugs to help the pain. Well I still had not started my period, and a friend told me that sometimes it can happen where you don't produce enough hormones to show positive on a urine test. I decided to take a HPT on June 16th. It was negative. Whats going on?? I have not been stressed or anything to cause a delay in my periods. So whats up. Now I have been extremly tired, with headaches, and a little nausea. But could that just be all in my head. I have a doctors appt, July 12th so we will see. However it is now June 25th I am 21 days late. I Hope I really am pregnant, but I refuse to get my hopes up, especially since I had 2 tests taken and both negative.