Holy shit. This sounds exactly like what I'm dealing with. Word for word. Came up out of nowhere, all of a sudden I smell like shit all the time, have the constant urge to shit 24/7 and it destroys my life.
I have gotten help from the doctors. I can tell you this right now. PLEASE go see a doctor as soon as you can. It can be nerve wracking but it is the ONLY way you can get relief. I am on my 5th year of experiencing these symptoms (constant stomach and abdominal pain, constant urge to shit, constantly smelling like shit). I have been prescribed anticholinergics to relieve my symptoms and they have saved my life. I was on the edge of suicide many times and was actually hospitalized and put in the insane ward for a night because I wanted to kill myself so bad and waited so long to get help.
Finding a solution is a long road that requires many doctor visits, but get a referral to a gastroenterologist as soon as possible. Having to deal with two short prostate exams was absolutely worth it so I could get prescribed medicines that helped me live a little.
I'm so sorry this happened to you. It's an awful experience, has ruined all my relationships and almost took my life. I wouldn't wish it on my worst enemy. I really hope you can find or have found a physician that can give you a referral to a GI doctor. I did it and it literally SAVED MY LIFE.
I just saw that your post was made in 2004. But it would be cool to hear back from you as this is the only post I've seen so far on the whole internet from someone with the same problem as me.