What causes stinky burps and gas?

I occasionally started getting really bad tasting and smelling burps along with an upset stomach and gas. Usually there is also loose stool accompanying it. The burps have to be the worst though, because they taste so bad I want to throw up every time I do it. They can last anywhere from a few hours to 48 hours or so. I thought maybe acid reflux but I no longer think it is that. Now I'm thinking its something I'm eating or drinking, but the only thing I'm consistently eating or drinking is Orange Juice. So unless its the OJ I guess it's something wrong with me. I also saw it could be some kind of parasite, but I'm not sure that's it because it comes and goes. Help :O