Q. My 2 months old baby is extremely agitated and not sleeping. Why?

Hello doctor,

My son is 2 months old. He is a normal healthy baby. I did not have any trouble with him so far. Sometimes, he will grunt and raise his knees to his chest when he has gas but has always been able to get a normal amount of sleep. Today, though he has been very agitated and alert, the whole day he has been kicking with his legs and flailing his hands like crazy. Extremely agitated I would say. He was hungry and ate a reasonable amount (he is bottle-fed), but the rest of the time he keeps squirming and kicking. He did not get almost any sleep for 12 hours so far. He falls asleep and wakes up every 5 minutes, with startling reflex, throws hands in the air and then starts to squirm and kick. Then cries and weeps and this keeps going. Sometimes, he just stares super alert and kicks his legs and arms for a long time. This is not a usual behavior. He occasionally has been like that, but not as much as today, and it never stopped him from sleeping. His temperature is normal (rectal 99.1 degrees Fahrenheit). His food intake normal. There is no vomiting or diarrhea or constipation. He never had colic. He usually sleeps 12 to 14 hours per day (7 to 9 hours per night). I am not sure about his problem. Can you help me? Does this sound serious? Should I go to an ER or is it likely something I can wait?