Got flu shot 3 days ago & have been sick since; temp.101, headache, chest pain, congestion, tightness & now started coughing & expelling some yellow sputum. is this normal? should i be worried? i feel absolutely awful.

Yes and no: There is no active virus in the vaccine but in some people it "stimulates" a memory and they can develop serious flu like symptoms. On occasion people with allergies to egg protein etc can have a reaction but it sounds to me like the former. Another possibility is a coincidental viral infection but in my experience it is the "memory" explanation that often explains best this phenomenon.