Hi M.,
First, there is a product called Colic Calm that works WONDERS! www.coliccalm.com
I used it with my daughter (after trying gripe water and mylicon) and it was amazing. I also recommended it to a friend of mine whose daughter was having SEVERE issues, and she too has found relief. So, that is something to help immediately.
Second, look at your diet. There are many foods that can cause irritation to baby's digestive system. Baby's system is still immature and is developing and they aren't able to properly handle (digest) some of the proteins, or acids and such that are found in these foods. When breastfeeding (and YEAH for breastfeeding!!!!) these proteins and what not get into your milk. So, baby DOES get them. And yes, it can cause gas, it can be reflux, it can be just simple irritation.
Some of the biggies for me were: tomatoes, anything acid ... like pickles, chocolate, milk, sugary foods.
I would try eating a very very bland diet. Seriously, I lived on potatoes and chicken for several months. Make sure you keep taking a good prenatal multi-vitamin so ensure you are getting all the vitamins and minerals you need and that baby needs. (it goes through your milk)
Keep in mind, if it is dairy proteins that are aggravating your baby, those proteins can take 2-3 weeks to leave YOUR system. So, by cutting dairy out you won't necessarily see results right away. Dairy proteins are very very difficult to digest ... consequently many babies have trouble with them.
The good news is, this typically only lasts 5-6 months. By 6 months baby's digestive system is more mature and can typically handle more foods. I was able to start adding foods around 5.5 months. (You will know immediately if it doesn't agree with baby. I typically found my daughter would scream and cry and draw up her legs within 1 feeding after eating the offending food item.)
So, you shouldn't be on a limited diet forever. Just a few months. But, the colic calm really does help tremendously.
You can also try laying her across your lap, belly down, and GENTLY bouncing your legs. A warm towel laid across her belly can also help relieve pain.
I hope your little one can find relief... and mama too! I know watching your baby cry like that can really break your heart. We went through it with our daughter.
Keep up the breastfeeding!!! It is SOOOO good for them!!!