My son has been a great eater (formula) for almost 4 months now .. just recently he’s super fussy.. turning his head back and forth .. legs and arms moving and forcing the bottle out then crying for it .. he’s been on 4 ounces sometimes if he wanted more I’d make 6.. every night he has a 6 ounce bottle and would take it with no problem now it’s like 30 minutes of him fussing while eating .. the dr laughed when I told her and she said if he’s gaining weight and happy he’s fine .. but like i said before he was such a great eater and would cry to eat every 2-3 hours now just doesn’t seem interested .. is this normal at this age or should I be worried ?