potty training regression

My son is 3yrs and 2months and has been fully potty trained during the day for about 11 months. However for the last month or so he is not telling me when he needs to do a BM and starts to do it in his underwear, he then sits down and strains as if he is trying to stop so I take him to the toilet where he then says he doesn't need to go or it won't come out (at this point there will either be a small amount in his pants or a fair bit). If I don't see him he still won't tell me he's done any until I notice but it looks like he's done the same thing, started but made himself stop before doing a full one. How do I stop this as I really don't want to place him back in nappies but I'm having to change his underwear between 5 and 7 times a day.

[Kevin Kennedy, Ph.D.]

Children who were trained as young as he was often show this sort of pattern. The behavior now indicates that he may well be constipated and it would be prudent to have his pediatrician take a look at him.