Baby awake too long at night

[Rehcallag14]

My LO is 4 months old. She is breastfed only. She isn't the best sleeper and only has 3 30minutes naps in the day. I have to rock her to sleep and then she goes in her crib. Fine. At night, she is fed and rocked to sleep. Then when we try to put her down she wakes or wakes after about 5 minutes. She is also awake for at least an hour between feeds during the night and then does a 2-3 hour sleep (once we finally manage to keep her asleep when putting her down). I don't have this trouble in the day. Any ideas or tips?
Thanks

[flanjabelle]

Have you read anything about sleep regressions? Four months is a prime time for a sleep regression.