You know, the same thing happened to me this spring and I was quite confused...and believe me, there was absolutely no possibility that I could be pregnant.
I had my cycle, and then 2 weeks later had another cycle...and then I went back to my monthly cycles of 29-33 days. I was under a lot of stress. In the past I had very wacky cycles where I could go for several months without one. The past couple years, they have been better, still with a 15 day varience (29-44 days).
What I decided to do, was just document it and see what happend. It hasn't happened since. Most websites I came across said you had to have a 4 month time period of wacky history before the OBs would start considering problems.
Menapause runs early in my family too, and I had the same though. If you are concerned, make an appointment. However, I would wait and see what happens within the next month or two; has long as you aren't having any other symptoms that are giving you trouble.
Best of luck.