Hello Sprinke, and welcome

I read your other post about PUPD, and since feeding and sleeping are often related, I will discuss both here.
I remember when Sebastien was 4 months old, and I knew all his 'issues' were related somehow (after reading BWSAYP) but I didn't quite know how to tackle the problem, until we figured out we needed him to be on a good 4 hour EASY routine and we kind of needed PUPD to get there.
I started PUPD with Sebastien when he was 4 months old, because he couldn't get to sleep on his own, ever, and he woke up very often in the night. I breastfed him every time because I didn't quite know what else to do. Because of his poor sleep, he was so tired that he would constantly fall asleep on the boob, therefore not eating enough during the day. Hungry babies don't sleep well, and tired babies don't eat well. So we had a sleep problem, and a feeding problem.
PUPD was extremely hard, but after a couple of weeks, he was sleeping through the night, and eating much better during the day.
This is where I get back to the topic at hand: When we started PUPD, we also cut out all the night feeds, and the use of the pacifier, all at the same time. Of course we made sure he ate enough during the day, by trying very hard to keep him awake during feeds. From this point forward, he only ate 5 times per day, including the dreamfeed. He was not 5 months old yet. My supply was fine, and I breastfed exclusively for 9 months.
If you decide to keep using PUPD but are finding it difficult, I suggest you read the success stories. They helped us enormously!