don't know who to talk to....

feel like I don't want to see anyone or go anywhere my baby is 4 weeks old now and this feeling is even stronger now. Even though I feel this way I still go out to make other people happy even though it makes me feel miserable most the time I'm there. I know that they are just trying to help and I do want the help I just don't want to be around anyone but when I am alone I feel lonely, lazy, tired, useless, not myself, and like I'm not a good enough mother to my baby even though she is healthy. All my feelings are all messed up because I want people around me, but when I finally have other people around me I just want to be left alone and not talk to people. I dont know how to bring it up to anyone...