What Do Prolonged Fever, Painful Eyes And Headache In A Toddler Suggest?

My three year old has been sick since last Thursday. Started with a cough and running nose. Over the weekend he became very tired, sleeping more than staying awake. He then developed a mild fever. Monday I took him to his primary physician. He at this point was barely taking fluids or wet diapers and diherra. He had a temperature of 104. Dr admitted him to the hospital. He was hooked to an iv and they did blood work, checked for strep, rsv and flu. All tests were negative and blood was good. They said he was dehydrated. We were discharged Tuesday. Since being home he hasn t improved. Complain on headaches and eyes hurting and can tell he s in a lot of pain. I took him to his doctor again and he s just having me monitor his fluid intake. if anyone knows their child it d be their mother and I know something isn t right with my son. Do you have any suggestions on what it could be or I should do?