Feel horrible....?

I feel horrible. My husband and I tried so hard for a baby, had such a tough time of it and felt so blessed to have our daughter, and motherhood isn't at all what I expected or hoped. Our daughter is perfectly healthy but has infant reflux and colic. She cries ALL the time and nothing I do seems to console her for very long. We're trying to get to the bottom of this, going to the doctor, trying medications and changing her formula. I carry her everywhere and rock her and swaddle her and sing to her...nothing helps and I'm so burnt out. Today I felt aweful for just putting her down and walking away for awhile...I'm alone all day and feel so frustrated. She won't nap and I can't even take the time to eat without holding her. I feel like a bad mom, I love her more than life but I am feeling resentful, particularly because my friends seem to have happy babies and I have such a miserable little thing! Any tips to get through this? I know it will end but she's only a month old now.