What should I do? Baby and relationship problems?

Our baby is 6 months old and my husband and I are having serious relationship problems. We used to be so happy, I just don't understand how it could have come to this. Although he loves our daughter deeply (that's plain for anyone to see) he has openly admitted that he is struggling to come to terms with being a father and the responsibilities he now has. He also says he feels left out. As a result, everything seems to be left to me and this makes me so resentful because he behaves so selfishly. I am trying hard to include him and get him involved with our daughter but he is always busy with something else and the second she starts to cry, he passes her back to me or just puts her down in her chair where she works herself up into a crying fit because he doesn't know how to deal with her. At the weekend for example, I wanted to have a shower so I asked him he if he could watch the baby for 5 minutes. His response was he is too busy and just leave her to cry! This is typical. Things got so bad a couple of weeks ago and I felt so tired from the pressures of doing it all on my own, I decided to leave with my baby and stay at my parents for a few days. I wanted to give my husband some space to decide if this family life is really what he wants because he just doesn't seem happy anymore - he is particularly unhappy with me and our relationship it seems and is constantly stressed. After some talking, we worked things out and I came home. Things were great for a while. He was helpful, happy and attentive and hardly put the baby down, but then a week later, he was back to his usual moody self. We're back where we started and I'm out of ideas. It breaks my heart because we used to be really happy and it breaks my heart even more when he complains about the baby crying or compares her to other babies who are supposedly better at sleeping at night or whatever. I just feel like he doesn't appreciate the life we have and or beautiful little girl and I just don't know what to do. I am starting to question the point in our relationship because I don't get anything from it right now and there are more times at the minute where I feel like I would find it easier and I would be happier on my own because there wouldn't be this stress. What can I do?