Lactulose is prescribed, and I think it is pretty well recognized by doctors. When I went to get glycolax (one of the cures people have found on this website), the doctor recommended lactulose, but I asked for glycolax. A couple of months later I went to a different doc (different clinic as well) because I was actually constipated, he opted for lactulose as well. So I don't think it would be hard to get.
The only times I can smell myself, I smell food, too. All I've ever heard is that I stink like shit, though. I don't think it's anything as serious as fistula.
I also have really bad problems with anxiety and depression, but that runs in both sides of my family. And I don't think I was really depressed until I found out I stink like poo. My dad and one of my brothers kind of stink though as well, but not like me. My brother will stink after a few days of not showering, while my dad is worse, and has really bad guts (years of a terrible diet), just like I do. But he's a stubborn old guy and you'll never hear him complain, and you'll definately never see him going to a doctor about it. I got cryptosporidium about 5 years ago, and that is when the funk took over(i think). I used to have constant diarhea and irregular bowel movements as well. Intestinew has helped that a lot. Also if you follow the diets that people talk about all the time here (lots of fruits and veggies, lean meats, and brown rice/potatoes for carbs) you'll notice a huge difference, not only in your stools, but also your energy.
You're probably right about the Serotonin thing as well. It doesn't matter what you read about staying healthy, minimizing stress and being happy is always a top priority. Whether it is the cause of the problem or just a huge factor, who knows?