Welcome. My daughter was diagnosed with enuresis and less often suffered from encopresis. We saw five specialists, none of whom could figure why she could not control her bladder and intermittently her bowels. We discovered some food sensitivities over this past winter, and she is now able to control both bladder and bowels. If you're interested in hearing what foods/additives were causing my daughter's problems, just ask and I can post more details. I have no idea if food sensitivities could be contributing to your encopresis and enuresis, but if you want to experiment with it, keep a food diary for four weeks, including the time you eat, what you eat, and the time you have an "incident". After a few weeks of keeping the diary go back and see if you can find a pattern--are there certain foods that commonly precede an incident.
Those with SPD that have a poor interoceptive sense often can't feel the urge to use the toilet until it's already out. There's a good article on this website about the interoceptive sense. There are many theories regarding therapies that may help with the interoceptive sense. One that we use is Therapeutic Listening. Another is Interactive Metronome Therapy. I'm sure there are others as well. Although we asked numerous times for our OT to address this area in therapy, she was not helpful in this regard, which turned out to be ok for us because it was food/additive related.