your blood test
report was normal?
if it is normal then probably you have been told anemic clinically.your period is brown.
it may be due to old blood in uterus.
that may lead to cramps.
may lead to weakness,irritability,fatigue
as such it does not lead to severe cramps.
yet as it decrease oxygen supply to all body parts it may lead to cramps.
but don't worry anemia can be corrected after proper evaluation.
you should consult a gynecologist for evaluation of cramps.
hope it will help.