I can't say for sure, but he could be teething and/or could he be going through a growth spurt...? For the teething, my doctor didn't like the numbing gels, so ask about Tylenol or Motrin? That's what I did when he got really upset like yours, NOT every 4 hours though, only as he REALLY needed it.
As far as the eating goes, are your breastfeeding? Either way, I would feed mine 20 min on each side and then give him a bottle of water.(He used to do what is called "comfort sucking" and feed for 45mins on one side if I let him! my dr. suggested water after 20 on each side. It worked! He drank fast and efficiently.) If he really eats, then feed him; he needs it. If you think it is more of a "comfort" meal, then give him water. I know it sounds cruel, but you need your sleep too. He won't wake up for water as much as he would for milk.
Everything I suggest is based on my personal experience with my now 28 months old son. Ask your dr. first though. I hope this helps! :)