I agree with what Missy said. I have taught KG and I really feel like you need to get him evaluated through the school district. They have some great services to help him get ready for school. I would check into this right away. My son started speech through the school district at 3. They really helped him out and he is was exited from the program when he was 7 after making a lot of progress over the years.
The school will not be able to wipe him and will expect him to do it on his own. There are some programs through the district for preschool children where they might be able to help him do that if he's unable to do so, but again, he'd have to go through an evaluation process.
Learning sounds like it's been a struggle at home, don't get too frustrated with yourself. There really could be more going on. I know this might freak you out a bit, but it's best to get things checked out before he's in KG because many times they can give him the services he needs to catch up, maybe even before KG...
I wish you the best of luck. Good job checking into all this now! :)