hi, my 4 month old has suddenly started screaming at bedtime. he is fine for most of his bedtime routine but as soon as I put him down to sleep in his cot he starts getting really irritated and within about 10 minutes is screaming. he has been like this for the past 5 nights now, and is taking around 2 hours to finally get him settled, even then this is by rocking him to sleep. we only started him on a bedtime routine about 4 weeks ago and he has always gone to sleep fine. sometimes he would take a while to settle but never screaming like the past few nights.
also, his daytime naps are quite short, he only sleeps for about 30 Min's at a time during the day, on a good day he might have one longer nap of around 1.5 hours in the afternoon but this doesn't happen often. I'm wondering if the short naps may be affecting his nightime sleeping? although he has never been very good with naps but still slept well on a night.

he is also waking up constantly through the night and crying, I've tried feeding him and he just seems to carry on crying after this. nothing seems to settle him back to sleep. we've resorted to putting him in his pushchair and pushing him up and down the past couple of nights but even in his pram he doesn't settle for more than an hour before he's awake crying again.

I am bf on demand so we don't really have a strict routine but I generally try to get him down for a nap after he has been awake for 1.5-2hrs, although he doesn't always go to sleep after this amount of time.
please help, not exactly sure how to get through this
