Meg, I have been following your posts about Coco and I don't have an easy solution for you (i wish i did though), but when you say she spends all night trying to poo and can't, maybe she needs a bit of gentle chiropractic work or a Bowen treatment (this is like a massage)? You had a very quick and early delivery and maybe something is out of whack with her.

I'd also try Tresillian and i really hope things will settle down for you both soon.