I'm just wondering if anyone has any ideas about what's causing this new fussiness and how I can get him to settle again?
I have a feeling this will be a long answer, apologies in advance. I will give this detailed answer thoyg h because it helped me to understand how and why sleep changed. Maybe it will help you?
Baby's sleep goes through various phases. The first phase is sometimes called the "fourth trimester". It lasts, give or take, the first 3 or 4 months. In this phase sleep is like it was in the womb. In that it's a passive state. Baby is used to feeling full, warm, comfortable, protected and subdued. Will wake when one of these needs is not met and then as soon as that need is met, should go to back sleep fairly easily once all needs are met.
Somewhere around 3-4 months sleep changed quite dramatically. Some people call this the 4-month sleep regression but I find this an unhelpful title because the word "regression" suggests that everything will go back to how it was if you just wait.
This is not a regression, it is a perminant change in sleep physiology. Sleep a stops being passive and becomes an active endeavour. It starts requiring active work to get baby to sleep. Sleep also starts to develop into cycles - with periods of deep sleep interspersed with light sleep. It becomes an active endeavour for baby to learn to stay asleep between these sleep cycles.
Sleep will never go back to being passive, that stage is now passed and will not come back. This phase will last as long as it takes for you to find a new way to actively help baby get to sleep.
Some ways to help baby learn to go to sleep are more independant independent and others more parent-dependant. Some examples would be
- sucking (breastfeed, dummy, feed to sleep)
- rhthymic movement (bouncer, pushchair, rocking to sleep, sling walks)
- Close/protected comfort (cosleeping, cuddling, swaddle, sleepyhead, patting)
There's millions more, you get the idea.
The next phase comes when baby learns to independantly link sleep cycles. Depending on how effective the move from passive to active sleep was will likely affect how quickly you move to the next stage of linking sleep cycles and sleeping longer.
Some babies will move seamlessly from passive sleep into linking sleep cycles so won't even notice a change. Other babies and parents will really struggle to find a way to actively get baby to sleep, so baby can't learn to link sleep cycles until they know a way to get to sleep. Therefore this phase has a wide time frame when it might last until, but usually linking sleep cycles happens around 6 months, but 3-23 months would all be normal for this phase.
Once linking sleep cycles, baby continues to need comfort of some kind to sleep until around school age. That might be independant comfort (dummy, comforter, self-movement) or parent-dependant comfort (cosleeping, cuddling, your presence)
So you are at the end of the first stage:
- Passive, newborn sleep, until 3-4 months
- Active sleep without linking sleep cycles, phase can last 1 day or 1 year or more
- Active sleep with comfort, linking sleep cycles. From whenever baby learns to link sleep cycles until around school age
- Adult-like sleep of tired > lie down > close eyes > sleep. With no props, comfort or help needed. Some research suggests this starts from around school age.
I'm just wondering if anyone has any ideas about what's causing this new fussiness and how I can get him to settle again?
Having answered the first part of your question, to answer the second part I would suggest giving all the help baby needs. Dummies are great, I would definately use a dummy.
You'll get a variety of opinions on what is best though. Some advocate no props and just pushing the is due and making baby learn quickly. That's not for me though, I don't like hearing a baby cry.
I would offer loads on independant help - dummy, swaddle, naps in something that moves, sidecar cot cuddles. Then once baby is going to sleep quickly and easily with props, begin to gradually withdraw them until left with just dummy for independant settling.