My suggestion is to go straight back to your GP and request to be put onto another statin.
Simvastatin did not suite me either, but its the first they try as it only cost a few pence to prescribe. I was then tried on atorvastatin and ended up on rosuvastatin. I was also advised to also take Coenzyme Q-10 as all statins block the natural Q-10 that is essential for muscles and that includes the heart. Since the change and addition of Co Q-10 the pains quickly eased and now I do not suffer any muscle pain, only generally from the pesky arthritis.
I buy my Q-1o from Healthspan because its easy to order and they quick to deliver (120 days supply for £10.95). To find Healthspan, simply Google it.