BF/BLS/Poo/Sleep?

I'm not sure where this question fits cos it is might be related to BFing BLS Poos Sleep or none of the above. I am trying to pay attention to what affects bub s sleep, and what her rhythm is, to work out where i can help her out. I have also been wondering if she is eating enough, and then also considering returning to work so am aware of how many BFs she has...

1) She was a regular pooper when she was exclusively BF. With introducing solid foods, this has slowed down and she strains alot more and gets tummy aches. I have a feeling she is getting dehydrated, but don't know how to get more liquid in cos she still has 3 or 4 BFs overnight and prob 8 during the day, plus drinks water. She went 3 days with no poop and then went twice today. Prior to this she had gone 3 days without and then had 4 or 5 poos in a day kinda like the first couple were blockages and then the next were more normal.

2) Once she has pooped, she then sleeps soundly. Today she had a 10 min nap at 1pm ish, awake and had lunch and then pooped. Awake all arvo then had a 20min nap at 5.30. awake had dinner, bath, boob, no sleep (though i tried) then had poop 8pm ish. BF and sleep at 9.30. She is still asleep now and will probably sleep well til 11 or so (going on past experience).

On days when she doesn't poop, she will either not go to sleep til 11 or 12 or will wake every 40mins.

Since she was little, she has never slept well if she needed to poop, and will sleep well after.

So, how do i help her poop regularly, given that i also will have to cut BFs down on some days (if i get some work).

I would like to reduce the nightfeeds, but if this is going to reduce pooping or lessen her sleep it's kinda counterproductive.

DO other bubs have poop/sleep links, or is there possible something else going on?

Have others found that starting solids leads to decreased pooping? Does this change as the tummy gets used to it?

Ta