salad i would get him checked only as he is 4 mths if older i would say he likes to hold on lol
Seriously which nappies do u use.... as i just changed my little man (3 wks old) and it was HUGGIES and they have a line that appears and the whole nappy feels soggy ..
If your little one didnt have a wee in a 24 hr period at all then i would have him checked seriously as that would be a concern.

Im not trying to sound obvious but you stated your stressed maybe your just not realising that he has wee'd on more occassions and the days you are really waiting for it it just wont happen on demand iykwim.

And another thing when he does wee is his penis red/raw and or does he scream ? As he may have an infection ??