Well, I cross posted this on the Phred touring email list and got two interesting replies, which I thought I'd put here as well for anyone else with similar problems.
First, this page was pointed out to me:
It looks like you can sign up and have a directory of English speaking doctors sent to you in 125 countries around the world. Could be very handy for long term travellers!
I also got this from a nurse:
"What you describe can be a very normal response to exercise, especially
daily exercise. Some women can actually go 3-6 months without having a
period. Other things that can cause extended time between cycles are weight
loss and hormonal changes. Unless you're having other symptoms, I wouldn't
get too worried about it. You might want to mention it to your doctor when
you get back, just in case they want to run any tests and be absolutely
certain there's nothing else going on, but as long as you're having normal
periods when you DO have them, you're probably going to be just fine.
For what it's worth, they even have new birth control pills now that will
stop your periods altogether. You use them daily for 6-12 months (I've even
heard up to 5 years), then you take a vacation for a few days and have a
menstrual period. I used to think it wasn't safe to go that long without
having a period, but they've done the research and found it didn't hurt