I am in the exact same position. My lo was 5 months yesterday and has been going through what I presume is the 4 month sleep regression for the past 3 weeks.
She has never been a good sleeper as she would always wake every 2-3 hours prior to this phase, but as I bf I always took it as part of the deal. However since the regression hit she on average wakes between every 40-90 mins, 6-10 times a night after the dream feed at 11pm
I've ruled out hunger as she rarely shows an interest in feeding before 4-5am, and I'm pretty much convinced the issue is her dummy addiction. I wish I'd never given it to her.
We tried to go cold turkey a week ago as I literally threw it across the room after the 20th+ time of putting it back in. I swear to god the hysterics we endured over that 24 hours were nothing short of rediculous and in the end we had to cave slightly just so that she would get some sleep. She doesnt even have it outside of bedtime, but she just will not settle without it
I've started trying to sleep coach her in putting her to sleep "sleepy but not asleep", which is completely hit and miss. Sometimes she will do it, others she fights it in a downward spiral. I've also started pulling the dummy out as she drifts off in hopes that she will become less dependant over time, but to be honest I'm clutching at straws now!
I just feel like such a failure at times, that I'm not giving her the right tools to be able to settle herself. I will keep persevering but I don't know how much longer my sanity will hold out!
If anyone has any tips I would also be grateful to here them, or share a bottle of gin!