Periods stopping while dieting/exercising. Should I worry?

[Whattodotodayhey]

I have lost quite a bit, 2st but I'm only just in the healthy range and have lost between 1-2lbs a week. Doing 20 mins hiit 4 times a week. Nothing extreme.... But my periods have stopped for the last two months. I did a pregnancy test (a few) just in case but all negative and we're not ttc.
Is this relatively normal?

Mine have done this a couple of times when I have upped my exercise (not excessively and still at the top of the healthy bmi range).
Quite disconcerting but nothing to worry about I don't think.

If you've been regular before it's usually a sign that your body fat has fallen below a certain level. I exercise far more then you and have never missed a period. You might want to get checked out...