Please see your doctor soon. If you are pregnant, then you have every reason to be excited. If you're not, you have every right to be sad. Make the appointment and find out.
I remember my mom (a little younger, but same "stage") thinking for a few days she was pregnant. At first they were shocked and really unsure about the whole thing... we were all "grown" and they finally had their time back. They went to the doctor together and found-out that she wasn't pregnant, but going through menopause. They were both very upset and sad... more upset that getting pregnant wasn't an "option" anymore than anything else.
On the other hand, my aunt experience the same "missed period" after being told for 15 years that they couldn't have children. She assumed that she was going through "the change" so she scheduled a consult with her doctor who had her take a test "to be sure". PREGO! They were over-joyed and shocked.
Could go either way, but if several tests have come back negative, my guess is that you are not pregnant. Call you doctor to be sure.