Re: Having my period for second time this month??
Yes, it's possible your cycles are starting to change at 37. This is not to say you are anywhere near going through menopause. Our cycles can start changing many years (10 or more), before we actually start missing them. I'm 48, and I noticed my cylces changing (getting shorter llike yours), a couple of years ago. It could have been happening before that, but I didn't notice, as I was very busy during those years. In reality, I never kept good track of my periods until the last few years.
If this continue's to happen, you may what to give your Doc a call, but since you were checked out in December, all is probably fine. By the way, hormone testing will not really show any significant change, until your almost done having periods. Mine have just started to change slightly, but I don't really miss a period yet, although I'm not ovulating regularly anymore.
I also can tell when I ovulate, and yes many times it's only a week after my period. Mine were also quite heavy for a couple years, and now are lighter, and only last about 3 days.
You might want to check out the menopause board, especially if you get other sypmtoms.
Hope this helps.