Hey hun I'm having the same issue with my little boy he's just over 4 months old, we've found changing positions helps or catch him when he's drifting off to sleep or already asleep. I follow the amount of 24oz-32oz which is enough. My little boy had 25oz today and is happy. I rang health visitor and they said as long as there is 6 wet/dirty nappies a day then it's no concern and that the soft spot isn't sunk in. So 5 x 150ml bottles in fine as its 25oz xxx
I wouldn't worry if he's still gaining weight. It's when he starts loosing it you should be worried. Just keep doing what you're doing