How much do you weigh, how old are you?
What did you weigh last year at this time?
The brown tint is from your thighs rubbing together. the crack in your crack is probably stretch marks from excessive growth due to puberty, or excessive weight gain. The skin doesn't grow fast enough, so it stretches, similar to stretch marks on a pregnant woman's abdomin. check your arm pits and directly in front of them on your arm, do you notice stretch marks there? If not, it could also be from over-exertion while trying to squeeze out a good sized log jammed up there. if you push with all your might (like in the "Misadventures of Shitman" video from "Green Jell-O" -later renamed "Green Jelly") you break yoru ass, literally. next time you get one stuck that bad, leave it in there and take some laxatives to soften your large prairie dogging friend. unless of course, you are mid "heave-ho" and there is no choice but to let it ride and feel the burn. Eat broccoli, drink lots of water, use unbleached whole wheat flour when you cook and eat 5 times a day, in smaller portions, rather than 1 or 2 times a day.
If you wipe and find blood on the toilet paper, or have a painful bowel movement, chances are, you have inflamed hemerroids. By all means, go to the doctor. I had a friend's mom die recently at age 50 because she had a flu, and was puking so muhc that she got dehydrated, and rather than going to the doctor, she just layed in bed, thinking it would pass, and instead, she died young.
I also had another friend, back when we were in college who thought he had grown a third testicle, and had bloody shit. he wouldn't get it checked out because he was sure it was cancer and didn't want to go to the doctors. he finally was med-evac'd to the hospital where he nearly died, because his third nut was actually a part of his intestine, which had tore through his muscles and was constricted. hernia...
at any rate, go get checked out. nothing to be embarrassed about. I love showing nurses my ass. it's the only time in your whole life where it will be ok to just drop your pants and stick your ass in someone's face and not get arrested. Doctors, medical assistants, and nurses have a good sense of humor about stuff, so don't worry. If you saw some of the stuff that they deal with, or hell, just crack open a nursing text book, and look at the pretty pictures. I guarantee they will be glad to see your ass compared to what the asses look like in those pictures.
Watson: R-- rubbing the clitoris, sir?
Humphrey: What's wrong with a kiss, boy? Hmm? Why not start her off with a nice kiss? You don't have to go ...