Help me please :( I'm so worried...?

I smoked two cigarettes about 3 weeks ago n then i suddenly fell ill, like i was coughing n i got a fever..then as soon as i began to get better n my coughing started to ease i smoked another cigarette n now i have these really chesty coughs with little phlegm coming out n iv been taking syrups but i dont thin they are doing any good. i am worried because sometimes when i breathe in air it provokes a coughing fit..n it's really bad..my back hurts from coughing so much..what do i do? :(