My cold wont go away...?

Ok so i've been sick for about 2 weeks or so. And I haven't improved one bit. Well the severe coughing has stopped but I have mucus on my nose and throat. When I cough I can feel it and I feel like puking because its soo nasty. Sometimes the mucus that comes out is greener than other days why? What does the color mean? And also sometimes when I blow my nose blood comes out. Because I go to school I walk around school a lot and lke when I get to cl im so exhausted..I have the urge to cough and cough. Why??