Child constipated after surgery

[SallyWD]

My son had surgery on Thursday and has been constipated since. I think he last went on Wednesday so it's been 4 days now. I know many suffer for much longer but today he's been utterly miserable. He's tried to go to the toilet several times and passed a small amount but is still very constipated and uncomfortable. It was so painful when he tried to go that he's now to scared to try again. He had urological surgery so can't really strain because it hurts his wounds.
I went to the pharmacist today and they gave me lactulose which they felt was the best option for him given his age and recent surgery. I've seen it can take a day or two to work. He's really suffering! Can't even sit down because it hurts so much and doesn't want to eat.
He's taken the medicine and I thought I'd take him to the doctor tomorrow if he's still suffering. Is there anything else I should do? He's drinking lots of water. Has anyone been in this situation with their child?

Do you have a stool or something to raise his legs whilst he sits on the toilet? It might make it easier for poo to pass

Yes we do still have one of those toddler stools he could use. I suggested this but he's now too scared to even try! What a nightmare. Just hoping the lactulose kicks in and softens it up so he can go comfortably.

that sounds stressful! Also a tip about constipation, tell him not to strain and just let it happen if he can

It sounds like he's sore...
Sudocreme or vaseline on the bottom can help x

How did you get on at the GP, OP?

Thanks for asking. I spoke to the GP on the phone and she suggested we give the Lactulose a little longer to work (can take 3 days which takes us to tomorrow). Definitely taking him in tomorrow if there's been no progress. Strangely he seems happier and more comfortable today. He's eating more. He really needs to go though!