coughing and congested baby

So my 4.5 month old daughter has been coughing and very congested for almost 2 weeks now. Just recently she hasn't been drinking all of her bottles (formula) and has been vomiting a lot of mucas with flem in it. She coughs so hard that she can't get her breath and then wheezes. She has a bunch of crap in her things. I can hear it when she breathes. She doesn't have a fever. Is there anything I should be doing? Does she need to see a doctor? Should I just let it go? Very very concerned about this.