Any suggestions?

What else could it be? I am on day 3 of missed period. Having period cramps, but no bleeding. Took 2 pregnancy test and coming up negative. Had a miscarriage 9 months ago and can't remember how I felt when I got pregnant that time. Giving it til Monday if i don't get period by then before I take another one. They say in some cases to wait a week after missed period. On some of the commercials that only 76% of women can get a positive 5 days before missed period. Anyway I really hope I am and it's not something else. I am 37 and my time is running out.