The writhing/crying sounds like colic to me (just a fancy word for trapped wind and your lo's guys not working properly yet!).
This typically gets worse from birth, peaks at around 2mo and is usually gone by 4mo at the latest.
Are you winding your baby well halfway through a feed and then at the end? Also, as colic tends to be wind trapped in the bottom end of her digestive tract, you could try 'cycling' or pumping her legs back and forth? Or rubbing her tummy in a clockwise direction? Or firmly stoking er tummy downwards from her nipples to the top of her nappy? All of these things used to help DS release a fart or two which seemed to help at the peak of his horrible colic.
Really hoping someone with more experience/insight than me might be able to help - feeling a bit confused and lost.
DD (9 weeks today) has always had quite fussy evenings - not colicky, just whiney, whingy etc. I know (well, read in a book) that that's normal for newborns, and she'd just stay up with us until about 10.30pm, cluster feeding, napping, whining again. Wasn't lots of fun, but fine. Her actual sleeping at night has always been good - will sleep for long stretches and settle quickly after night feeds.
In the last 10 days or so the fussiness was being topped off with a couple of hours of really inconsolable sobbing which nothing would stop. I thought she was perhaps getting overtired, so I moved her bedtime back a couple of hours, to about 8.30pm.
It's worked OK-ish, in that when she falls asleep at her new bedtime, she'll still sleep for long stretches, but it's done nothing to rectify the sobbing, which now just starts earlier in the evening! It's heartbreaking listening to her cry like that, and I just don't know what's causing it.
The other thing is that when she was going to bed at 10.30pm she'd settle really quickly - just have a feed, fall asleep while feeding usually and then go down easily. At 8.30pm it's taking her a good hour to settle with lots of angry crying and writhing around, and when she's feeding it's frantic sucking/chewing which is a bit alarming (not to mention painful!).
Does anyone have any idea what might be causing it? If she was overtired why is she finding it harder to fall asleep at the new earlier bedtime? Or have I not moved her bedtime early enough?! I just don't know what to do for the best. So if anyone has any thoughts, please share them!