D.B.
Could be any number of things, from the stress you mention to possible peri-menopause. Another not-so-uncommon occurrence is an anovulatory cycle, meaning you just don't happen to produce an egg. That's not necessarily related to menopause - it's just "one of those things." So if there's no egg, there's no follicle to release the hormones that control the cycles, and there can be an additional build-up of endometrial tissue (lining of uterus) because there's no "have a period, now!" notice. So, periods are late, and BTW they can be extra heavy/crampy when they finally come. Not dangerous, and your pregnancy tests will come out negative. I'm not saying this is what's going on, but my guess is, if you call your doctor, you'll get the "wait a week and let me know" sort of answer. I'm not saying that's what it is, just that it's a possible, non-urgent situation. Also, double check the one-kidney/one vas connection. And vasectomies can fail - it's not common, but it's possible, and it was in your husband's consent form.