Hi M.,
I am also a new mom, breastfeeding a 3 week old. Because I am a bookworm, I read all sorts of things before having Meg about breast feeding. I have not experienced, yet, what you are describing with your daughter, but the La Leche League book on breast feeding says this is normal for exclusively breast fed babies. I was also told this last week from a friend who has a 3 month old boy who was only going #2 once a week. Her pediatrician said that breast milk is used very efficiently by the body and therefore leaves little to be expelled. Also, breastfed babies will not get constipation; so there is no worry of that.
Gas will make anyone cranky and it could be a result of something you are eating that is not agreeing with the baby. I am also having this problem at the moment. At the suggestion of a pamphlet on breast feeding from the hospital I am keeping track of everything I eat or drink as well as when Meg is fussy. On the left side of the paper I write the time and everything I put in my mouth. On the right side I write the time Meg eats and the times she is crying. By doing this I may be able to see if there is something I'm eating that is affecting her. It says I may need to go back 2 meals to see anything. Citrus fruits, garlic, peppers, spicey food, and chocolate are very common "problem foods." I'm wondering if it is kiwi or chocolate. I had no idea either of these might cause gas.
You might want to contact a La Leche League leader in your area. They are very knowledgeable on everything related to breast feeding and more than willing to help at any time. You can find them by going to their website http://www.lalecheleague.org/ click "find a LLL near you."
I hope you soon will experience primarily peaceful nights and days.
Blessings on You and Baby Girl,
D. B