Two little words have saved my life with my 3 month old breastfed baby - gripe water. It's actually a product called Baby Bliss Gripe Water. Basically, it is a mixture of fennel and ginger that helps ease digestion. It also keeps my daughter regular. I give her a teaspoon twice a day (you can give it as frequently as every 4 hours) and it helps tremendously. My daughter has had a bunch of tummy problems - sensitivity to milk proteins, reflux and just general fussiness. Within 20 minutes of taking the gripe water, she is a new baby - and she absolutely loves the taste. They have a website: http://www.blissbymom.com/?gclid=CMm3lffByooCFQQRYwodMibngg where you can find out who carries it in your area. In Beaverton, OR, we get it from Segal for Kids at the corner of Scholls Ferry and Murray.
I want to add that we use the gripe water in addition to me being completely off of all milk products (including anything containing whey or any milk protein). In addition, she is also on zantec for the reflux. We spent weeks experimenting with the right combination to keep my daughter happy and the gripe water in addition to the other two make for a much calmer and happy baby.
I hope this helps. It has absolutely saved our sanity.
Best wishes for reduced fussiness!