L.P.
He may be teething. If you think this may be the problem, try a little clove oil on his gums. The numbing affect may calm him down. Plus the oil smells so nice!
But if the fits are so long as you mention it may be something else entirely. My son went through a tantrum phase for a bit. And what I was told was to ignore him. It really worked for me. I would totally pretend not to hear or see him. Then he realized that screaming wasn't getting him any where and stopped.