DD is 18 weeks and seemed to be getting really good at sleeping but all of a sudden she will only nap for about 20 minutes to half an hour unless I'm holding her and at night she's waking up every couple of hours and is really difficult to settle back down. Anytime she does spend sleeping in her cot, she's constantly fidgeting, thrashing about and kicking her blankets off. I just lie there listening to her knowing she will wake up soon or worrying she's cold. Every night between about 12 and 5 in the morning we're up and down with her non stop. I have wondered if it's teething as she has some of the tell tale signs but have also read about sleep regression at this age? Sorry for the long post just looking for some reassurance that it will get better, I'm exhausted!
18 weeks is about 4 months, right? Classic sleep regression. It's a biggie too - it's because they're becoming much more aware of the world around them, etc, and it's hard for their little brains to switch off. It will get better, I promise. DD had an awful regression from 3.5-5.5 months, but slept through (7-7) from 8.5 months. I rode out the sleep regression - bit of co-sleeping (we had her in co-sleeper crib anyway), learnt to feed lying down and every time she woke up I just fed her back to sleep. That was what maximised rest for us in our house. Just do what you have to do to get through it. And perhaps try a sleeping bag rather than blankets, as she won't be able to kick that off?
Then at about 5.5 mo I did very gentle sleep training - basically helping her learn to self-settle and stopped feeding her to sleep at bedtime. Then shortly after that we moved her in to her own room and I put limits on when I'd feed her (i.e. not before 11pm and then no sooner than every 2.5 hrs, or something like that) and sent DH in to settle at other times. Gradually, gradually things got better (with a few set-backs here and there). By about 7 mo she was down to one or two wake-ups. And slept through from 8.5 months.