Being a day care teacher, I have seen this type of behavior before. The first thing that comes to mind is, has he been in daycare for a long time, or is he just starting? Another question that comes to mind is has he recently changed rooms or teachers? I ask these questions because that when I have typically seen those types of behaviors.
If he has been with the teachers in the same classroom for a while, he may be going through separation anxiety. He is at the right age for that to be starting now.
When I was working at another facility, we had a little boy who did the same thing. He would scream until he was put in a crib to sleep, and then would wake up the same way. It was almost impossible to get him to eat too. What we did was have mom fix him some of his favorite foods for us to feed him. This worked at least to get him to eat. Then as for the crying, one of us would focus on him as much as possible, while the other was able to tend to the others in the class (of course that only works when there are two or more teachers in the room though).
It sounds like they have made up their mind about your little man. Which is sad in my opinion, because he is just a baby. I would see if there is a way that you could observe the classroom, like the other poster suggested. This way you could see what it is that is going on. That is really the only way to know if there is something wrong, or if they are not giving him the attention that he needs at the right times. I know some centers have closed circuit surveillance camera's in the rooms, where parents can sit in another room and watch, that would be ideal in this situation but I know not every center has them.
I would ask that the teachers document everything. Buy a small one subject notebook and put his name on it, and ask them to take notes about his behavior throughout the day. I would then start doing the same thing at home, document everything. That way when you do go to a doctor, if you decide to go that route, you have documentation from both places. Make sure if they do agree to do it, that get the times in their notes too, as that could help with determining if there is a problem.
I know this is long, but it might help!
If you have ANY questions please feel free to contact me privately!!!