You ARE forming a habit now, but an excellent one. You are establishing a wonderful, strong nursing relationship that many women struggle for. Your daughter easily latches on and stays on. Not only is this "normal," it is desirable. Personally, none of my three kids ever used a pacifier. A pacifier is a fake nipple. Just give her the real one and then you won't have the habit to break later. It is your job right now to be a human pacifier. It's your job to comfort her.
Next, she IS eating for nutrition, not just calming and sleeping. Her tummy is tiny right and frequent eating is needed.
If you feel you need support from other mothers who nurse on demand and co-sleep, there's a mother's group here this friday and the first friday of each month:
http://www.bodymindandspiritabq.com
Support from like-minded moms would really benefit you and give you confidence to continue doing what you feel is right. And what you're doing IS right.
As your baby gets older, you can do things to teach her fall asleep without sucking. But right now, she is so very young and her only jobs ARE to suck and to sleep.
One last note, breastfeeding makes for strong and proper jaw and teeth development. Pacifiers and bottles won't necessarily ruin this, but do not encourage it as nursing does.