Hello Lollies
You are not alone! I'm having a similar problem with my dd. Long story, unfortunately, but it shows how her stubborn character reflects on the entire potty training process.
She just turned 4 in August, potty training started at age 2.6 (Easter last year) as she was dry at night. After a completely exasperating period of holding onto wees for record lengths of time and then wetting herself, she eventually gave in and started using the potty for wees in October last year, with a little help from nursery, which began when she turned 3. However, she then remained clean and dry at nursery but the whole of her time there, didn't use the toilet once during her morning nursery sessions.
During all this time, she continued pooing her pants, usually at a set time during the day, and they tell me that she needed to be changed. You'd think sorting this out would be a doddle, but no. Like your little boy, she wouldn't say she needed to go, would not be persuaded to sit, bribery didn't work, I just had to keep on changing and washing pooey pants.
Fast forward (or rather, painfully slowly forward) to Easter this year, when she decided that she didn't want to poo at all, and started holding it in, resulting in skidding on pants, sore bottom, more witholding vicious circle. However, by the beginning of summer (age 3.6), she had begun to understand bribery, so when she had dirtied her pants, I cleaned her up and left her (bottomless) in the bathroom, playing with a sinkful of warm water and floaty toys, and the warm water on her hands would relax her enough, that she would actually go herself on the potty, and get a potty prize as a result. She would be very proud and managed to stay clean and dry for about a month and a half as a result. still would never admit she needed the toilet, we would always have to look for cues, but I thought I'd work on that over summer.
Then we went on holiday mid-July. She was ok for the first week and a half, using various toilets happily, but then she started witholding again, so I just bought a packful of sanitary pads to cope with the skids, and managed to get through the holiday with my sanity reasonably intact, but bothered that I had to keep putting her in a warm bath to help her to 'go' after a couple of days witholding.
Anyway. She starts big school on Monday, is is still witholding, and I am becoming very, very nervous. Have seen the GP about this, has said that she'd refer to a paediatrician, still waiting for that.
However, in the meantime, I found this useful article and I shall be following the advice.
Everyone says "Oh don't worry, she'll be ok at school" but they don't know the half of it. I feel like a failure as a parent because she's going to school not potty trained properly. btw, I have an older son who was textbook in that regard, so I'm not a complete novice.
As the saying goes, you can lead a horse to water, but you can't make it drink. That is certainly true with regards to all aspects of my dd's potty training!