I think it sounds like teething personally. Have you tried giving him something like a frozen flannel to chew on? Or a teething ring that has been in the fridge? Has he pulled or poked at his ears at all?

Paris went through this on and off a lot! And whilst it stressed me out at the time all the Dr's and hospital said to do was just wait and see, if she wanted a bottle let her have it if she didn't then don't push it. If there were signs of dehydration or she didn't drink within the 24 hour period then bring her back for observation but it would always pass within 24 hours. Or to keep an eye out for fever or rash.