My 7 week old is demanding more formula. but i'm scared in case health visitor states he's over weight. what should i do?

Don't overfeed: You need to add up what he is taking in 24 hour period. He should be consuming 32-36 ounces in that time, absolute max 40 ounces if he is not spitting up ANY of the formula. That is enough calories. He may want to just have some sucking time.You don't need to feed him every time he makes noise - there can be other reasons for him to make noise. He may also be getting ready to start sleeping nights

The average volume : of formula/feed is age in months + 1. If you recognize & respect his cues for feeds, demand feeds should be fine. If the interval is short, offer a pacifier first till ~ 4 mos. Set a consistent bedtime & routine. Read, rock, wipe out his mouth with a soft cloth after feeding, then put him in his own bed, drowsy but awake, to self-calm for sleep. Make sure he's fully awake before night feeds.