Constipation in toddler disrupting sleep. Advice needed please!

[Posey]

Ds is 21 months and has never been a regular everyday pooer. Hasn't caused him a problem until recently (well I think this may be the problem).

Have been keeping a bit more of an eye on things recently and a pattern seems to be emerging. This is it in a nutshell:

Day 1: Does a big poo in the morning. Eats well all day, very cheery, sleeps well that night.
Day 2: No poo. Still cheery enough. Sleeps okay.
Day 3: No poo. Bit of a grump at times. Eats badly. Sleeps appallingly. Very restless, rolling onto tummy, clambering on top of cuddley toys etc in bed. Often awake for a prolonged period during the night.
Day 4: as day 1

Would seem to be related wouldn't it?
He eats a good diet (usually) with plenty of fluids, fruit and veg, raisins etc.
Can anyone help?

BTW we're on day 4 today so after a c**p night last night I'm feeling hopeful for tonight (please follow the pattern, darling boy, I can't cope with another bad night

By my calculations you'll be on day 4 again today. Have you been to the drs at all?? Might be worth going for them to prescribe you some lactulose which may regulate your ds. It may be worth trying some freshly squeezed orange juice and water 1st though. My sil tried this and it worked a treat, unfortenly it didn't work for my dd so we ended up at drs. DD problem was a bit more than just constipation in the end. I don't want to scare you, she was going weeks without a poo.

Thanks for replying.
As often happens when you think you've seen a pattern, it goes completely arry. We had a really crap night after an otherwise typical day 1, but then we've had 3 great nights.
Have upped the fluid intake and encouraged more fruit which seems to be helping the constpation.
Will keep an eye on things though and thank you for your thoughts.