You may want to check with your doctor regarding your periods. I too had similar situation and found out that I have PCOS. I hope you don't have that issue, but you would be better informed about the problem if you check with your doctor.
I did asked my doctor specifically that what would qualify as excessive exercise - she said more than 1 hour per day.

I've heard this can be normal for women who exercise a lot. Are you trying to get prego? If not, I'd enjoy the break. I have an IUD and for the last 4 years have had no period...but now with frequent hard workouts I now have periods...so who knows. I guess our bodies just freak out sometimes. If you feel great and have no other symptoms, then I wouldn't worry. If pregnancy is in your near future then I'd make a plan with the doc.

this may be a silly question, but have you ruled out pregnancy? it's the first thing that comes to my mind when someone misses a period (or four).

Check with your doctor. It is probably nothing but any time you have a change in cycle for no known reason you should check.

Your exercise does not seem excessive to me, but different people react differently. Weight is not nearly as much of a factor as bodyfat

I'm about 5'3" and when I got below 115, I ceased getting my period for about 18 months. (I had an eating disorder with an exercise compulsion, that's how I managed that.) It didn't resume when I eased up on exercise, not until I'd gained about 20 pounds. At the time, the doctor said it was my low BMI rather than my activity level, and my experience seemed to bear that out. Don't know if that helps.

Everyone else in my life was more freaked out about it than I was. Frankly, I considered it convenient not to have to worry about the mess & the products & the bloating, cramps & weight gain -- which is probably not a healthy attitude, but I wasn't very sane back then, really.

Well your BMI is in normal range and that's usually what would **** with a period. I would take a pregnancy test (if you haven't already) and consider what birthcontrol you are using as well (I have the implant and my period goes missing sometimes I quite enjoy it when that happens). But yeah...Best go to the doctors because it could be a sign of something more serious and it's best to catch it early.

Also, congratulations on your weight loss and I'm in awe of how much exercise you do. I am so lazy compared to you!

I don't think you're exercising too much or eating too little, but missing your periods is not a good thing. Check with your doctor...

I havent had a period since last July.... I even went on a 6 week long "REST" where i didnt train AT ALL-- still havent got it back....

To put it in its most simplest, basic terms--- Your body is stressed. VERY stressed. Stressed enough that all "unnecessary functions" have ceased in your body. Your body is smart enough to know that at this point in your l ife, RIGHT NOW, you have NO business supporting another life growing inside of you, because frankly your body cant even support itself.
Take it for what its worth, but know that the longer you go without your period, the more likely you are to *damage* your body.....more prone to stress fractures, early onset osteo problems, problems concieving (if you ever want to)..... The doctor can give you a 10 day round of progesterone to *induce* your period, but that doesnt mean it will continue again Regularly.

From the looks of your stats, it appears you have been dieting down for a LONG TIME...give your body a rest.... as SOON AS you start eating at maintanace you WILL GAIN BACK WATER WEIGHT. We are talking 5 ish pounds. This is your TRUE weight....that is the weight that freaks people out, because they think its fat. Its not. Try and remember WAY BACK to when you first started losing. You may have had an initial big drop the first week or so. That was the water coming off, and it WILL COME BACK. Accept it. You cant live your life in a deficit.
And FYI, as soon as i stopped obsessively exercising, i started dropping weight...FAST.... like 7 pounds in a matter of a week or two......

Google "Leigh Peele" and "Metabolic Repair Manual. It was written for women such as you and I.....

I don't think your level is excessive, but your body may react differently, so you definitely should see your doctor. There are A LOT of reasons that your body might skip a period that have nothing to do with your exercise levels. So talk to your doctor, both about your eating/exercise levels and anything else going on, and get this checked out.

Not a silly question at all! I should have mentioned that there was definitely no chance of pregnancy.

Honestly, I had the same thought for the first month or two. I was almost glad for the break. The longer it's gone on, though, the more I've started to worry.

Thank you! But don't put yourself down, fellow chick - you're not lazy! I am, if anything, a tad obsessed.

Thank you so much for this post, mkroyer. I've read through it a few times and everything you've said makes sense to me. I have indeed been dieting down for a very long time (since July 2007, when I joined 3FC), with only a very short break in 2008. The question of whether or not that might be/have been a bit much stress for my body has crossed my mind quite often in the past few months. I will definitely spend more time looking into Leigh Peele and her Metabolic Repair Manual. I only had a chance to skim through her site earlier today. Out of curiosity, have you ever used her Metabolic Repair Manual?

Ladies, thank you ALL very much for your kind words and suggestions. I appreciate both. I think a trip to the doctor is in my immediate future - just to be on the safe side.

Lovely-- i actually JUST FINISHED her Metablic Repair Manual. 2 weeks ago? I dont want to post my life story here, but i can tell you it was probably the best gift i could have given myself...... would love to talk to you in more detail about it if you want....ive been working with Leigh Peele... she has a no-nonsense, no-BS approach to everything, so i apologize if i said anything a little too harshly!

I have PCOS. My periods are so irregluar its ridiculous. However I found out I have a thyroid condition. Anyway once I started changing my lifestyle and exercising, aunt flo decided to grace me with her presence!!!! So you never know!!!!

It's possible, but impossible without seeing the doctor.

I went down to 109lbs at 5'5 (yes, 109!) from too much exercise and too little food (no ED, just clueless as to how to get the athletic look). I still never lost my period, even getting down to 15% bodyfat (which is extremely low for women!). Even some female bodybuilders get down to 8-10% bodyfat and never lose their periods, but some women at 20-25% can lose it.

Our bodies just react so differently!

I haven't used Leigh Peele's book but I have heard nothing but good things about it.