I'm an average-sized, 27 year old female, and for about the last 2 days I've had a really weird pain just slightly above my belly button. It generally seems OK when I'm sitting or lying down, but it is really painful when I'm standing or walking. I also noticed that next to the spot where I'm experiencing the pain, there is a strange 'dent' in the skin that was never there before... it looks like a line, about an inch long. Someone at work suggested a hernia, but I don't see or feel any protruding lumps. Just the strange dent. I generally feel OK otherwise, aside from an incident yesterday where I suddenly felt very overheated and queasy while grocery shopping. Any thoughts on what could be causing this pain, and on if I should go to the doctor or hospital?

Sounds like your gall bladder and yes go to doctor or emergency room.