My 4 week old baby whats feeding constantly and wont settle?

i have a 4 week old little girl she is my first baby. I am finding myself constantly feeding her this is mainly at night and she wont settle, ill wind her to make sure this isnt a problem but she just cries wanting more milk, she then over fills herself and throws up then i have to start all over again. what can i do???? and is this normal?