If the transmission is popping out of gear, then it's likely to be an internal problem that requires a partial or full rebuild. Check the trans fluid level and at the same time, feel for metallic grit in the trans fluid. If the syncro teeth are damaged, the trans fluid will probably feel gritty.

The second question?
I've never I had my bowel movements stutter, so I can't speak to that problem.
I'd go see a proctologist...since it sounds painful.

But...if you're talking about your car, then I'd like to know what's going on when the car stutters. Does it happen at or near idle...or when you're rolling along at highway speeds and try to accelerate?