New member - Poo holding - is GP the next step?

[CannPPPP]

Hi, My son is 3 and 3/4 and we're having issues for nearly a year now with toilet training. It took 4 months to get there with wees and I admit I wasn't paying attention to the poo part as I thought that would take longer, so probably missed the holding.

The situation we have been in for a while now is that he will hold it in and not go. I thought it would sort itself out in time with encouragement, reward charts and occasionally laxatives (lactolose from the chemist) but this isn't the case. Currently he is going up to 5 days without pooing and having wee accidents and some poo accidents due to this. He will sit on the potty for hours in the day but just nothing happens. Occasionally after a long time sitting he does a big poo and seems ok with this, not upset.

I wasn't sure what the next step is that we should try? Is this a trip to the GP? I've been a bit hesitant to go to the GP as I thought they might be dismissive but I can see some of the posts on this site that this might be the next step. Could anyone advise? Thanks!