I too had that problem with my 4 month old! She usually has the sweetest temperment and when she was 3 weeks old, she started doing the same thing.. just so beet red in the face and had terrible gas and reflux! I couldn't even hardly leave the house because she threw up so frequently. I did some online research at breastfeeding sites. Two things that worked for me:
1. cut out all milk and heavy dairy products (I still did small amounts of cheese) I wasn't lactose intolerant, but SHE was! Her father was too at that age and had to be on Soy formula (which in itself can cause problems for some boys)
2.) This REALLY helped: Your breast milk has 3 parts to it, the foremilk, which seems more watery and is what comes out with your letdown. the mid-milk (dunno the technical name) and the hind-milk or back-milk, which has the most fat and fills the baby up or tells him that he's full. the Fore-milk is VERY lactose heavy and also contains the hormone that makes them fall asleep. I was trying to nurse like I did with my first, which was equal time on both sides. My cousin (a real lactation consultant) suggested that I just feed one side at a time. It seemed that my baby was getting too much fore-milk and all that lactose. When I switched to feeding one full breast at a time (although I was lopsided) it make a HUGE difference in the reflux and gas pains!!!
The last resort I tried was to invest in some "Colic Calm" gripe water. I had to get it online and it was quite a bit more than the gripe water at the store. But its SOOOO worth it. Mylicon drops only treat the gas at the top of the stomach, but not the intestines where most gas it. I found it online, it has vegetable charcoal in it, so its BLACK, but don't be alarmed, it really really works and my baby loves it!
We hardly have to use it anymore.
My 4 month old is finally outgrowing a lot of that, but still is gassy. But she's not in pain and that's the most important thing!!
Good luck!