Lac1961 my adopted son with SPD was not potty trained till he was four. And even now at nearly six has difficulty with it. He occasionally has accidents but it is not laziness. Been there done that. Tried bribery when younger and praise etc. I don't think the feeling of wanting to go is there until it almost happens. Then it is a dash to the loo which he doesn't always make.
At the moment his fine motor skills is a problem too and wiping his bum is a difficult task. At school they seem to think he has mastered it cos he doesn't shout them anymore. Well I will tell you they are wrong, he does have a go in school but sometimes it ends in an awful mess which he doesn't tell anyone about. I discover it or sometimes he sheepishly says he has poo in his pants.
I have come to terms with him having trouble and we get on with it. He always looks upset and sorry to be in this situation. I just hope one day he will be able to do it and not shout me to come wipe him. He usually does it when I am eating my dinner or cooking . Please stick with it and this forum is good, the people on here are truly helpful. You sound very stressed to me, don't let other people close to you, who don't understand what it's like, make you feel you are doing wrong just cos most kids manage it, our kids ARE special.