AIBU to change night feeds and co-sleeping at four months?

Just have him in bed (safely - lullaby trust guidelines), C curl around him and feed to sleep the whole time and leave him snuggled against your boob. Anything else means a hell of a lot less sleep - which is remarkable given how little sleep you get anyway, but if it's a little sleep or no sleep I'd take a little sleep!
He's much too young to try and reduce feeding him.

The baby is 4 months and supposed to be fed on demand, whatever the method. In the middle of the night breastfeeding is easier than formula feeding. You are getting over 5 hours from 7pm which is a great stretch at that age, sometimes people hear about sleeping through and think all babies should.

I co-slept and found that easier but it's not for everyone.

A four month old baby needs feeding to their schedule not yours
ie on demand

This! Cosleeping (whilst always adhering to Lullaby Trust guidelines) has been my sleep saviour with my two EBF DCs. It can be hard sometimes that when they’re small they rely on me so heavily to sleep but it doesn’t last forever and you’ll treasure the experience when it’s gone x

100% put down in cot until you go to bed, then cosleeping the rest of the night. So much more relaxing. You don't have to get out of bed for feeds, can stay lying down etc.

Just co-sleep /bedshare from first wake onwards. Or for all the night long whichever is easiest. Follow safe sleep seven rules. Join laleche league for support. (And coffee and cake) also FB group “the beyond sleep training project” is good for peer support (with no sleep training suggestions) look up dr mckenna’s breastsleeping. Remember numerous wakes to breastfeed are normal and protective against sids.
take naps with your baby in the day if you can. Appreciate this may be hard-I’m on my third baby so not able to do this any more sadly !
the first stretch of sleep overnight can be the longest. Make sure you’re in bed yourself and sleeping for this. this season is all about survival.
breastfeeding lying down in your bed at night so you don’t have to even sit up yourself. Have your bed safely set up as per safe sleep seven rules. Cuddle curl position.

Solidarity. My son (now 3) was exactly like this.

I have a four month old now (5 months next week!). She used to do a nice stretch 8.30-2 ish but last couple of weeks the first stretch is only 8-11. Then we cosleep, lots of nursing.

She's my third kid, and after the first I pretty much gave up looking into regressions - it seemed to be the common answer for everything always! My only advice is hang on in there.

Maybe consider putting him to bed a bit later to try and push back the 5 hour sleep stint so that you can also get some more solid hours of sleep before the first wake up? My third was not a fan of an early bedtime which meant a lot of cluster feeding on the sofa during the evening but then she went to bed at the same time as me and we both slept for a long stint. Good luck!

You talk about comfort sucking as though it is not necessary. You could introduce a dummy, if you feel that way, but I wouldn't advise it. Breast feeding is so much more than food for your baby and prolonged sucking allows your body to absorb baby's saliva - which is how your milk composition adapts to baby's need. It also builds up your milk supply so that when the growth spurts get going, you will produce enough to fuel that period of rapid growth.

One idea you might wish to consider, could you delay that 7pm feed and 5 hour sleep (by 15/20 minutes per day), so that you feed just before your bed time and have a 5 hour break then? Then, as others have suggested, bring baby into bed with you for the rest of the night. I know that your current arrangement gives you some baby free time while you are awake (and many mums love this), but you are paying for it by not getting enough sleep. Is it worth it? Only you can decide.

Whatever you decide, hang on in there. I remember how hard it is, but it does pass ♥️

Echo co sleeping. I did the same with DD2. She only slept properly when next to me. I just couldn’t keep going being up and down all night without any decent sleep - one night I fell asleep sitting upright feeding her and gave myself a huge shock as I had let go of her when I nodded off and she had rolled down me and was face first in my lap. We obviously had a guardian angel that night who woke me up and she was thankfully absolutely fine. After then, I slept with her next to me following guidance etc.
I actually used to go to bed with her at 7.30pm for the night as I needed the rest. She slept through at about 8 months.
I promise this will get better!

Too young for any sort of weaning or dropping feeds; safer to do that from 6 months, but not at 4.

Also if he reliably sleeps until midnight that’s really good. I’d make the most of that and go up yourself at 9pm to get some decent sleep before he first wakes.

I loved our next to me cot with our third baby because I could lie with my arm on him but not worry about squashing him or sleeping awkwardly. He knew I was there but I had my own space too. And for feeds I didn’t have to bring him into bed with me or move him afterwards, he could just stay in his cot and feed then I would ease myself gently away. Not perfect, but I definitely got more sleep than with my first two, who had separate cots. I was so knackered by that point! The down side is that he still climbs into bed with me even though he’s at school! I agree about trying to get some sleep in that early stretch of his, much as it stings to lose that free time. I found even if I did this a couple of nights a week it made a difference.

I had one very bad sleeper and one very good sleeper. Even the good sleeper wasn’t great between 4-6 months. I co slept with them both then moved to their own room at 6 months and sleep improved from there (bad sleeper was still up 3x a night for feeds until 16 months good sleeper was up once initially then slept through 12 hrs from 8 months). At 4 months I think they still need night feeds but don’t be scared to try something different, if it doesn’t work it’s just one night and you can go back to what you were doing.

I always found the 4 month sleep regression the worst as you just feel like you’re getting into the swing of things and then you’re back to what feels like never ending feeds and constant waking. I promise it’s just a phase and does eventually pass (even though at the time it feels like it might go on forever)