DS is almost 4.5 months. He occasionally sleeps through, but most nights will wake for a feed once between 1 and 3 am, depending on when he went to sleep. But I'm now getting more nights of 2+ wakings. Tonight its been wake ups at 9 and 12 already after going to bed after the 6 pm feed

Just Christmas night he slept through, and only single wake ups the next two nights.
Is it normal for babies sleep to be so erratic? I never know what to expect. And my breasts never have time to get used to a pattern either! Sometimes more feeds follow a day when he's fed poorly, he's become very distractible, but this is not always the case before some of the more wakeful nights.
For some reason, I'm finding it harder and harder to go back to sleep myself, so sometimes I get no sleep at all between wake ups. Which increases my frustration.