feeling helpless

Baby Fisher is now almost a month old. He is only gaining 2 oz a week though, and hasn't made it back up to his birthweight. I have been exclusively breastfeeding since the beginning. My doctor doesn't seem too terribly worried but I'm starting to feel hopeless and helpless and like a failure. Thinking about just switching him to formula at this point even though it's not what I want to do. I am so lost at this point