Dear A.:
My kids weren't overly picky, but truly I gave them so many choices on one plate as toddlers that I didn't need to worry. In other words, something on the plate was bound to appeal to them... a mini buffet if you will. Every meal was "snacky" and came pretty much right out of the fridge. A typical terrible two meal would be:
3-4 grapes
1 slice of avocado (high in fat)
2 slices of cucumber
half of a pbj
1/2 slice of deli meat
1-2 cubes of cheese.
1 dixie sized cup of juice
They ate what they ate. If they left the meat and the avocado it was such a small portion, that I would have their left overs as a snack, or I simply chucked it. I never made a big deal over what they didn't eat, nor made eating an issue. For instance, I only offered them between meal snacks as a question - not a visual offering. And even if they requested yogurt or spaghettios, it was only a small portion served with other things. Every meal was variety centered.
Also, I never worried whether anything was kid food or not... because I really had no idea where their taste buds would be at any give time. If I had it, I put one or two on the plate. At one point I had a toddler that liked marinated mushrooms, and the other liked manderine slices. Very often they surprised me as to what they preferred. Even now that they are older there are "kid foods" (like mac and cheese) that they don't/won't eat.
Another thing I did was something someone else mentioned... I made the food fun. I cut things into shapes, arranged foods into crazy faces (boats, cars, etc), and drew smiley faces with squeeze butter, catchup, and so on. I took a few extra minutes to make meals colorful and happy.
I noticed you said "glass of milk". Is it a sippy cup or a water sized glass? The amount of milk might be filling his little tummy up to the point there is no room for food. Also, I hope you are giving him milk with fat in it. Kids need that fat, unlike us adults who are better off with skim.
I truly do hope you get him eating. I can't imagine a mother in the world feeling great about having a kid that is below weight. It would panic anyone. But you need to relax. Remember, since you are obviously stressing out and he is feeding on that. This could be turning into a means for getting your attention.
Good Luck!
Y.