I also totally sympathise, my dd 2.8 used to be a brilliant eater but is now very fussy, she eats quite a range of foods and they're all very healthy, so I try not to worry too much. But she won't eat a "proper" meal, anything like shepherds pie, fish pie etc she won't touch, and absolutely nothing in a sauce. She hates anything on her plate to be touching anything else. She only really likes to eat lots of bits of things eg her ideal meal would be some ham, grapes, cottage cheese, apple etc, all on separate plates (makes for a lot of washing up!!)
I try not to let it bother me but if we go out with family for a meal, or to someone else's house i feel embarrassed that she's so fussy. We went to my mum's last week and she had made bolognaise and pasta, my mum couldn't understand why she won't eat it and she thinks I shouldn't let her be fussy. But I really don't want food to become an issue and I know it's just a phase they all go through.
Dd frequently goes to bed having eaten no tea whatsoever , but then the following day will make up for it by eating loads. I don't think they have the same habit yet as we do of eating more or less the same amount at each meal.
My philosophy now is:
here's your meal, eat it don't eat it but there's nothing else, then I make a point of enthusing with ds (14 months and a great eater so far) about how yummy it is, all the while chatting to dd about other stuff.
We try not to have any dramas or tantrums even though it's so frustrating when you've spent time making something.
Try to just chill out about it, you're not alone, and as long as he's healthy that's the main thing. It won't last forever and gradually he'll start to try new things.