He has always been a great eater - would eat anything put in front of him, though not in vast quantities. But for the last 3 weeks he's refused anything cooked - he simply shakes his head and pushes it away without touching it. He eats a big breakfast most mornings, and will happily eat bread and cheese and fruit and frozen peas for lunch and tea, but almost anything else gets pushed away. Thinking back, he had ate a large bowl of meatballs and pasta on Boxing Day and some fish fingers two days ago, but that's it. He's drinking lots of milk, and has eaten his own body weight in mince pies over the festive period, but I stopped giving him junky snacks a few days ago to see if it improved his appetite, which it hasn't.
I'm just not sure what to do - his sister used to be very fussy but is a lot better now (nearly 4) and as I am cooking for her anyway, I figure I may as well keep putting stuff in front of him. I just don't know whether to then offer him things I know he will eat, or just say "that's tea, if you don't want it that's fine".