Could be colic! Buy Ridwind and put 4 drops in baby's milk or directly in his mouth. See instructions. My boy had colic, went to see a PD, he first check if there's any rashes on his body and if there's my hair on his toes or hands (very dangerous if there is!) and found nothing wrong so he said might be colic. He was okay after a day of taking that. Could also be growth spurt. This phase is very frustrating for every parents but do be patient as it will go away on it's own. Try to cuddle and rock baby or even swaddle him.
Christabel Soh