To think he should have got this by now?!?

[SometimesMyMumComesOutMyMouth]

My DS is 3 (4 in August) and off to school in September.
We potty trained him for wee's in less than a week and he has been dry for nearly a year day and night but he just does not get pooping!
It's got to the point where DH and I are at the end of our tether. We've tried praise, not getting cross, getting cross, ignoring it and just cleaning him up and starting again, sticker charts, rewards, iPad time on the toilet etc but NOTHING seems to work.
We've taken him to the doctors and they have said he's not constipated, not withholding so it's just something that will come in time.
But seriously how long will this take??? School have already said that he needs to be toilet trained fully by September otherwise when he continually soils himself it will result in one of us having to go to school to deal with it (the occasional mishap they will deal with).
Currently his nursery are very good and just change him and support us in what we are doing but today is a prime example where he has gone through 7 pairs of pants!
AIBU to be at my wits end with this???

What does he say when it happens and how do you handle it?

I ask because my dsd has issues at nearly 11 still and we have all tried so hard with her. She tends to be worse when unsettled ie this week when mum has changed contact so she can go on holiday and leave the kids behind. Mum shouts and screams, we do the talk to her route calmly and try and find the cause.

Not sure what you can do to force it as my dd (2.10) just got it all on her own we really didn't have to do a lot