Maybe I can advice thee a good way to try, which isn't dangerous
I remember one time I went for a bike ride. That day, I was a bit desperate to go poop. The sit was a bit uncomfortable and I kept moving a lot, so once I went back home, I had some skidmarks in my underwear.
Maybe thou couldst try eating a lot of fiber one day. After that, drink a lot of water and go for a bike ride.
If thou gettest lucky, thou won't last much time until wetting and pooping thyself
Beware of pee holding, it can be bad for thy bladder.