There are some good homeopathics for teething. Try Hyland's Teething Tablets or Boiron Teething Capsules. Since they are homeopathic, they don't have any risks or side effects. Hyland's even makes a homeopathic teething gel, which is safer than the Orajel. Be careful with dosing him with Tylenol or Motrin, as it can cause stomach bleeding. But if the baby needs to sleep, you can slip him some occasional Baby Motrin - just be careful with it.
You have the right idea with cold cloths before nursing.
Remember that teething can also cause stomach upset. You can try Gripe Water for the upset stomach. I prefer Wellements Organic Gripe Water for Colic. They carry it at Mt. Hope. It's water, ginger, fennel and chamomile.
My daughter started teething at 4 months as well, and it took months for the teeth to actually break through. Just hang in there. Keep on breastfeeding, it's the best comfort you can give him right now. And remember that this is only temporary. It will pass. Good luck!