I haven't changed my bed sheets in over 6 months

That isn't healthy, please go wash your sheets. You don't have to get crazy about it, but it won't kill you to throw them in with the wash. Especially if you've had things like crumbs every other day, just take care of yourself. All that bad smell is loads of bacteria building up from a lack of changing. Stuff you sleep on. Even forgetting how it smells, you'll probably just feel better too when it's cleaned. Consider cleaning the mattress beneath at this point too, it's probably soaked through.