how can a get my 20month old to eat?

Welcome to the Terrible Twos! There are probably a few different things going on with your son right now. First of all, he may not feel particularly hungry most of the time right now. Kids go through phases where they eat less but that will change right before his next growth spurt. He's also trying out his free will. He realizes that there are choices and he is trying to make his own whenever possible, which in the case of most two year olds is to not do whatever it is you want him to do. It would be nice if he sat down and had a normal meal but, since he's not interested in doing that right now, you're going to have to work with him so that he gets the nutrition he needs. If he only wants to snack, let him but make sure he snacks on healthy foods. Give him choices so he feels like he's making decisions and let him help prepare his snacks whenever possible. Even a two year old can help peel and cut up a banana with a plastic knife. My kids liked chicken nuggets and they come in fun shapes these days. Let him help you cook something as long as it's not anything that will splatter. Don't worry, he won't be in this stage forever...then it's on to the next irritating one.

Is he having trouble with teething, Lou? Sometimes that puts children off eating for a while. I found it was pretty common with my four that they had phases of being fussy about food. The clinic nurse used to say no child will let themselves starve as long as there's food on offer - so I tried not to worry.