Firstly Hugs, it's never easy when they are young & they don't sleep well
It says she has to be sleeping 5-6 h stretch and trough the night after 3 m and she is absolutely NOT!I seriously don't know what do I do wrong.
Secondly "she hasn't read the book" neither of mine consistently slept 5-6 hours under 6mo, some babies don't - which makes it hard when books make you feel they should.
In terms of swaddling, I swaddled both mine until it basically got too hot & as we didn't have Air con - that meant 30C plus here otherwise I think I'd have swaddled past 4-5mo & 7mo with both mine.
Has she recently got more hungry as there is a big growth spurt around 4mo & that can mean that babies feed a lot more than they were a few days earlier.
I'm wondering if you get the 20min naps if you put her down after less than 2hours OR if she is like my DS2 who would only 'tell' me he was awake when he was bored looking around the room, it was only when one time I was up with a sick DS1 that I discovered DS2 was awake at 5am & so the next morning I checked & he was the same, even though he didn't make noise until after 6am he'd been awake much earlier & so I needed to put him down for a nap earlier.