7 weeks old baby and still has a lot of mucas or is she congested?

my 7 weeks old baby sounds like she is really congested... i don't know if she has a cold or is her mucas. she threw up 2 days ago while i was feeding her... i was sooo scared... i didn't know what to do.. i thought i was giving her too much... she's taking a little bit less than 4 oz right now. what can i do to get rid of her mucas?? will it go away soon?