K.B.
M.-
I have the same problem with my 4 year old daughter. She will say "I'm not smart", "I can't do anything right" and the worst was the first time I heard her say "I don't like me". I couldn't believe I had heard her right.
Here's what I have done and so far it seems to be working. First of all I praise, praise, praise her for every little thing she does. When she has helped me with the baby or helped me clean up I make a big deal out of it and tell her I don't know what I would do without her and that I couldn't have done it without her help. Throughout the day when I have a moment with her I tell her I have a secret for her and then whisper in her ear how much I love her or tell her how beautiful she is or how smart, etc. At bedtime I always remind her of something that she did that made me particularly happy or proud of her that day. I am also trying to get her to tell me something that she is proud of herself for as well.
Good Luck,
K.