How do you clean up a messy, filthy room that a old dog likes to use as a bathroom so you can have people over?

Hi, My room is messy, and I don't mean paper, trash, clothes, and stuff everywhere dirty like everyone else's room, I mean all that and more dirty. I have not cleaned the thing in about a year, my moms dog likes to "visit" every once and a while to leave her "peas and carrots", and the bad part is that every other room in the whole entire house looks even worse than this. Even the basement, which I am to scared to visit when my dad is home. Even rooms I never go in look like this, so I think I have some of work to do unless I add a door to my room, which we all know is never going to happen. I need to get everything out, including the smell of it, which smells sorta like a combo of one subway (the entire store, not just one sandwich), mildew, 1000 male cats, and a swimming pool full of a female iguana's urine... Oh, and just a hint of BO.