Weight lose and menstrual cycle changes? A little TMI...

Mary
Since the end of 2015 I have lost about 60 pounds going from 379 down to 318.8. I went from not knowing if my AF was going to come to it coming every two weeks now. It's not as heavy or normal like it's more brown old blood than it is fresh Blood, if that makes sense. I'm on birth control pills as well. I also I a very high stress job and home life, neither one is changable. 
Has this happened to anyone else that may have lost a lot of weight this fast? 
Should I be concerned and go to my OB/GYN?