Confessions from This Nursing Mother (Revisited)

I planned to nurse my baby for a year; I don't think I am going to make it. My baby is 7 months old, she loves soilds and doesn't see to like even being latched on any more. I feel like my supply is down and she doesn't even care to stay on and help get my supply up. She nurses and then cries. I felt so bad that I offered her a bottle and voila! that's what she wanted. My poor hungry baby.
I am really depressed about all this. That I can't produce enough to satify her or not caloric enough. She still fits in most 3-6 months clothes since she is still like 14 lbs. She hasn't reached double her birth weight, which babies are supposed to reach by 6 months. Everyone comments on how tiny she is.
 I tried so hard to make it. I really struggled around 4 months and somehow survived on about 5 hours of interupted sleep as I tended to her hungry cries, hoping to get my supply up. I took Fenugreek, an herb that helps boost your supply. It worked for a little bit. But truly my breasts haven't felt really good a full for a few months. I use to wake up full but now I can go 12 hours between feedings and not feel much difference. I know that she gets feed and satisfied sometimes because I can hear her swallow and she is a very happy baby.
I am sure I have done something wrong like letting her have a pacifier and giving her a bottle at night. Yet many other moms do this and still nurse for a year or more. I feel guilty and angry and sad.  I don't understand why I could be a "strudy mountain women" and push her out drug free but not be able to nurse her for a year.  I put trust in my body to do it but now feel like I was forcing something that wasn't meant to be.  I tried so hard and now not to make it to a year, I feel like a failure.  What was the point of trying so hard just to come up short in the end anyway?
And now I have to buy formula....great.