Cough is not a side effect of this medication but you are way over the maximum dosage and need to address "why". Good luck.
Fisrt I'd like to question why your doctor has you on 150mg a day of simvastatin when 80mg is the maximum recommended dose. If it was me, I'd be asking!
If you've developed a cough that is not associated with an upper respiratory infection, a cold or seasonal allergies, you should have it evaluated by your doctor, especially if you're experiencing shooting pains in your head when you cough.
I'm not saying you should be "worried" per se, just smart. Get it checked out.
Peace
Greenlydia