Hi Crystal welcome! You certainly have your hands full! It's good that you know he has SPD and that's probably the main reason for his delayed potty training!

My two sons are 10 and 6 1/2. Older one is officially diagnosed (when he was 6), younger one unofficially (and more mild). My older one was delayed with all his milestones, including potty training. I had no idea about his SPD but looking back I'm sure he either didn't feel the sensation of needing to go or didn't connect the sensation and going potty. We struggled with it from 30 months to 47 months. I tried every trick I could think of. Nothing worked. He was night trained before he was day trained. After my younger son was born, I sort of gave up. I just kept bringing him to the potty throughout the day and encouraging him to use the potty--praising him when he was successful, not making a big deal when he had an accident. We went on vacation right before he turned 4, rented a condo in FL for a week. I showed him where the bathroom was just in case he needed to use it. A little later when he was playing while baby brother was napping, he hopped up and ran to the bathroom. He had a few accidents after that but for the most part he started going to the potty on his own after that week in FL. So it really wasn't anything I did (at least that I know of), he just did it when he was ready.

My younger son was easier. I waited until he was a couple weeks before 3 years old. With the help of his daycare provider, he was trained in 2-3 weeks. But he'll be 7 in September and still wears a Pull-up at night. Bed wetting runs in my family so I guess we'll just have to wait for him to grow out of it.

I remember how frustrating it was. Hang in there! Try to bring him to the potty at set times every day. Some people call it the before & after rule. Before going somewhere in the car, after you get home. Before going in the bath, before going to bed, etc. Praise him if he's successful.

Good luck!