K.Z.
I have a 19 month old son and he's a pretty picky eater, too. It's totally normal for toddlers to start expressing their opinions and desires with food right around now. And to be honest, it sounds like your son has a pretty good diet if he's eating cheese, bread, veggies and fruit. My son won't eat any plain meat, but he will eat chicken nuggets and chicken tenders with ketchup. He also loves eating pancakes and waffles because he can dip them into syrup. Have you tried any of those foods? Dipping is fun for toddlers - my son loves to dip things into salsa, salad dressing, and of course, ketchup and syrup. I also recommend V-8 juice (great source for veggies and vitamins) and peanut butter (if you haven't already introduced it to his diet, it is another great source of fat and protein).
Toddlers will eat when they are hungry, so don't worry if he doesn't eat a lot during one meal or throughout a day. My son hardly ate anything yesterday, and today he's already eaten enough to feed a grown man!
I would also try to start slowly weaning your little guy away from the bottle, if you can. He's a big boy now and should be drinking from the cup.
My best to you!