My oldest son struggled with solid food for a long time. He would want to drink fluids constantly. There were very few foods that he would eat. We now know that he is on the Autism spectrum, which can cause them to have problems dealing with textures and tastes. He also had ongoing medical issues that were obvious which were contributing to it at that time. He is now 18, and still takes in a lot of fluids, but he also eats plenty of food.
I can tell you from our experience, the more we tried to push food on him, the less he wanted to eat. It became a power struggle. It only got better when I left him alone. I kept good foods available to him and offered it to him. I also had him drinking Carnation Instant Breakfast or Ovaltine in his milk. But I didn't try to force him to eat. As his health improved, he naturally started eating more. A doctor told me that a small child will not starve themselves to death. They will eventually eat.
It's scary, I know. I was also always worried I would be reported for neglecting him, like they would think I wasn't feeding him. Just try to stay calm about it. The more relaxed you are, the easier it will be for you child to get through it.