Your DD is over-tired. Good sleep promotes better sleep and unfortunately for you, poor sleep results in even worse sleep. So because she is so exhausted and over-tired, it is perpetuating her poor sleep.
Babies (and toddlers) cannot self-sooth in the way an adult can (tired, lie down, close eyes, sleep) until school age. Until then they will need something to assist them sleeping.
You have developed feeding as that sleep prop and as you have found, feeding to sleep is not a brilliant long term plan. So you need to teach your daughter other ways to get to sleep. Other sleep props include:
- Dummy
- Thumb/fingers sucked
- Muslin sucking
- Special toy
- Special "blankie"
- Patting
- Tickling
- Rhythmic movement (bouncing, rocking etc)
In your position I would go whole-hog with all possible sleep props and then gradually reduce to one or two when baby is sleeping better.
Dummy Babies are naturally routine creatures. Your son will naturally develop his own routine.
The problem when you don't have a routine is you tend to swing from one extreme to the other, exhaustion and over tired, rather than striking the happy middle.
Once in a routine you don't need to wait for tired signs, you know baby will be tired at a set time so you put them to sleep. If you wait for exhaustion to strike (like falling asleep in middle of a bottle) then baby has been tired for a good 60 minute previously so you could have put him to sleep an hour earlier than you did.
Dummy & bouncy chair is my favoured no cry sleep solution. Add a muslin or toy squashed against face, maybe some patting and shushing. Then just bounce, bounce, bounce that baby rhythmically into sleep oblivion.
Typical routine. My DD is 5 1/2 months and she sleeps for 2-3 hours at 9am, 2 hours at 1pm, sometimes has 45 minutes at 5.30pm (sometimes not). Bedtime is 7.30pm, feed 11pm, up 7.30am.