Talk to Pediatrician on Tired When Sleepy

Hi. About one month ago my 3.5 years old got chest infection, dr gave him antibiotics and he went fine. When he was taking antibiotics he used to cry after 1 hour of taking Antibiotics/panadol saying that he is getting tired. His condiotion used to last for 5-10 minutes. I thought may be he felt dizzy due to medicine thats why he says so. Anyways after that he got better.

Now the problem is he has started saying that again. Especially when he is in bed trying to sleep and when he wakes up early and still sleepy. He cries and cries and keeps saying he is tired. He gets better afyer 5-10 minutes. I am unable to understand what is this. He was never a cry baby.

I called GP and she was of no help. She refused to do any blood test until any other symptom appears. I am at my wits end. Please somebody help me what it can be and why he is saying so. I am going mad everytime I hear him saying this I feel I am having panic attack. Please help me please