If you are drinking caffienated drinks that can cause her gas big time. I hate to say this but I gave up breast feeding because with my daughter who had a very sensitive tummy I was basically on bread and water after eliminating everything. It was tough! At about 3 mos I couldn't do it anymore. I couldn't eat salads unless it was basically iceburg lettuce, I couldn't drink milk, I couldn't eat dairy, almost everything I ate bothered her. I talked to our Pediatrician and we put her on Nutramigen formula. It is predigested and so much better on their systems. My daughter thrived, I mean gained weight, was so much happier so that choice ended up working for us.
I am not suggesting stop breast feeding, but each child is different and if she has a sensitive stomach, you need to take away dairy, caffiene, too much sugar or anything you are doing now and see if that helps. Process of elimination in your diet.
You can pass on the caffiene if you don't wait the two or three hours you should after drinking it. Talk to your Pediatrician. Make sure it isn't reflux either, which is basically worse at night when they are laying down longer.
And feel blessed you had a baby that slept through the night so young! Neither of mine did until almost 10 mos!!!!!