My son was like that when he was little, and I know what you mean about getting worn out. I have two opposing suggestions. I used to feel like I wasn't getting to do anything, and would feel worn out that way. wearing her around in a sling so that she can nurse and you can go about your business might help when you're feeling like that. Sleeping while she's nursing is also a good way to go.
Sidenote: When my nipples were really sore, I found out (a month in to it or so) that I had thrush, and I had thought that it was maybe just from him nursing so much. So I could have saved myself a lot of headache if I had gotten that checked out first.
I made some suggestions, but I also gotta say: enjoy it while you can. I look back fondly at the times when he'd nurse for an hour and I could just curl up with my book and relax. Now he's on for two minutes and rushing on to something else. Newborns are demanding in some ways, but very relaxing in others.