nursing strike going on 7 days

I am sitting here with a pump attached to my breast wondering if I will ever be out of this prison. Every since Levi was born he has had trouble nursing. First, with latching on (he lost a pound in his first week of birth and I had a lactation consultant come help). Once that resolved itself the fussiness began. Every few weeks he will go through a week or two of fussiness when nursing and I can't figure out what the problem is. Every time I have gone to the doctor to rule out any medical causes, and there have been none. So now it is the end of day 6 of this particulary period of "strike" I guess you can call it. I haven't gone to the doctor because I assume that it is just as before. The only thing I can think of is that he nees more milk and isn't getting enough because he will try to eat and within a minute the crying and fussing begins. I have done what they tell you not to do and have given him a bottle with either pumped milk or formula or both, because I just can't stand for my baby to be hungry and I can't take any more of being home alone all day long dealing with it. I am too tired. The question is, how long is long enough before I give up? Is it really worth it to keep nursing him if we are both unhappy? Can I deal with the guilt and the(perhaps unwarranted) shame that I know I will feel if I give it up? Can I even afford to buy that ridiculously expensive formula? For now, I guess I will just keep trying to feed him any way that I can. I know this is personal stuff but I just had to get it down and wanted record of it for the future. I'm off to bed where I will finally get relief from the feelings of anxiety, worthlessness, inadequacy, sadness, and guilt.