S.V.
you got good advice already but i know what you mean with it being frustrating. my son also has a late july birthday and my sister but it nicely when she said remember he is a young 3. although your son is comfortable with the potty he may not be fully ready. you said he did good when he didnt have pants on most likley because if he started to pee he could feel the dripples. ditch the pullups it makes it so much easier they feel the pee and then can start to really make the connect of what it feels liek when they have to go. My son would do the same thing with the pullups we could sit on the potty forever and as soon as we were up and pullups on he would be. so frustrating . What worked for us was ditching the pullups and i just paid close attention to him for about a weekend to see what clues he would give before he had to be and try and to catch before he went but oh man if he did go when he has his underwear on he knew and would RUSH to the bathroom. Give it time i think my son was starting to really get it about 3 1/2. just curious when is his birthday mine is july 29 . good luck with the training trust me it does happen even though in the moment it feels like it never will.