This is a common question I see with new parents and it has two answers. Firstly at 4 months it is quite common for babies to need extra nutrition, this is offered in the way of introducing solids along with still breast feeding. This is a controversial topic in parenting at the moment, because basically there is a number of recommendations that solids should only be started at 6 months of age, however 10 years ago babies were routinely introduced solids at 3 months of age. The change in recommendation was due to theories about allergies. At the moment the majority of paedtricians are recommending solids at 4 months, and recent research has showed the theories around allergies to be in fact the opposite. The later delay in solids, the greater the allergies.
So my recommendation at this point is that at 4 months of age, if you havn’t started solids then it is more than likely that your son is hungry. This could account for his ‘acting hungry’. I would breast feed first and then offer solids.
The second part to your question is that how your baby falls asleep becomes his sleeping cues. This means that his brain cements in a list of ‘how I need to go to sleep’ cues, and when he wakes during his day or night sleep, he thinks that he ‘needs these cues to return to sleep’ thus he calls out to you to do ‘whatever’ it is that you did for him for him to fall asleep. I teach parents how to have independent sleep cues which means that your baby can go to sleep independent of you rather than dependent/needing you to do ‘something’ in order for them to get to sleep. Essentially if you comfort nurse him to sleep then sucking will become his sleeping cue and his brain cements in this cue that he needs to suck to go to sleep, the same process works for rocking, holding, wrapping, music, wearing or relaxing by himself. So which ever cue you use as his eyes become heavy and he falls asleep and they close for the last time, this will be his sleeping cue. I recommend parents have cues that are ‘independent’ of them, which means their baby doesn’t require them to do something to get them to go to sleep, so if this is what you want, then as his eyes start getting heavy and closing, take him off the nipple and place him to fall asleep in his own sleeping place, independent of you.