Hello, I Was Wondering About My Bowel Schedule. I Apologize

Hello,

I was wondering about my bowel schedule. I apologize for the word usage but this is awkward enough. :) So, I rarely poop every day or even every other day. I have been able to poop around every 4th day. Sometimes, it takes me a week. When I finally do go, it's hardly an accurate amount for how long it's been. About every two weeks, I will have a bad couple days of diarrhea. It smells like burnt hair and it's dark sometimes but bright green other times. (That could possibly be because of my vitamin intake) I take a multi every day along with a biotin. I'm a social drinker and not very social. I don't take any prescriptions other than my birth control. I am a daily tobacco user. I'm 26 years old and I'm 5'6 and I weigh 150 lbs. It's suspected that I have endometriosis but I was informed that that cannot be verified without an exploratory surgery. I have had abdominal pain to the extent of an emergency room visit on 4 occasions and I have been sent home with laxatives once (a big jug with some powder and I had to mix it with water and chug it every ten minutes). The other 3 times they attributed it to my suspected endometriosis. I feel ok except for the obvious discomfort of a crappy poop schedule (haha). I would like to know what's wrong with me. I feel that once I'm asked about my uterine issues, they stop trying to find out if there could be another reason. If you could maybe gimme a nudge in the right direction, it would be much appreciated.

Thanks for reading. :)