DS2 is only three at the end of this month but I'm wondering if anyone could shed some light on this.

I'll go back a bit.
About a year ago now he had a rectal prolapse.
It was straight after a bit of a tummy bug or something, or so I'm assuming, he seemed fine but had a little diarrhoea.
The rectal prolapse was frightening and not knowing what it was or what to do we ran off to A&E. The didn't exaclty know what to do either and it was outside his body for a long time at this point. Eventually they got it back in and sent us home.
It happened again that night. DH wasn't volunteering to pop it back in so I put in a pair of latex gloves and did the job.
It was easy enough.
it happened a few times within the next moth and in that time we got a referral for Westmead hospital.
These appointment don't come round fast so I happened about a dozen times in the meantime. By then, DS2 was unnerved by it and a pro at squeezing it back in with my help.

We just had our follow up appointment about three weeks ago.
In the 6 mths between the two visits to the paediatrician, it rarely popped out at all, but in the month before it began happening a bit more often.
I took a photo to show them and told them that while he's unphased by it when it happens, he is holding his poo to avoid using the potty at all.
More of a head thing that it hurting I think.

Anyway, they asked if there was any cystic fibrosis in the family, kind of freaked me out. I thought that would be pretty obvious from birth no?
So I asked is that a concern, ah no...then why worry me???
They then asked if he had a lot of diarrhoea.
he didn't, like I said he was holding his poos. Which by the time he couldn't hold them anymore they were massive, and probably making his condition worse, but still no diarrhoea, until easter weekend that is.
He ate far too many eggs (on the sly) and ran the stomach out of himself.
Still no prolapse though.
But all week his poo is getting softer and softer then yesterday omg!
Puddles of it all over his room!
I showered him off, threw his clothes in the machine, gave him a drink and just watched him.
He seemed fine, he is a little more tired than normal lately but otherwise happy.
I got up this morning and DH said he was up at 2am bringing him to the potty and his guts ran out of him again.
Same thing. Only H actually puked in is own mouth with the smell.
Said he never encountered anything like it. Now I owuld brush it off as a m an thing but I've noticed that too, getting worse through the week.

Anyway, now I'm worried so considering the questions they asked me.
Of course it's another 6 mths before we see the paediatricians again and I can't just call up. Ridiculous when ye have concerns.
I have him booked in with the doctors first thing Monday morning to ask for a sample to be tested for a bug, parasite or I don't know, allerigies?
I just don't know.

Anyone had something similar happen?
Does it sound like lactose intolerane by any chance?
Is there anything else I should be asking to be tested, bloods maybe?

I want to be prepared for Monday and not come out thinking I should have done more.