Re: First post, it's an embarrassing one... Time to talk poo!
I had this issue about a month or two ago, and it lasted a couple of weeks. I'm not 100% positive of what it was in my case, nor if it is the same pain you are experiencing. As with all things, it is best to seek a professional to be sure.
That said, I believe what I had was a nasty hemorrhoid, and it definitely could be what you are feeling. They are not fun.
For some peace of mind, a doctor's visit would be best, but the likeliness of it being something terrible at your age is very slim.
Good luck and feel better!