Can I still take simvastatin 5 months after the expiration date?

You really need to consult your doctor or a pharmacist.

The rule usually is the medication is good for one year past the expiration date.
This depends on where the medication has been stored and also the stability characteristics of the specific medication.

You're probably OK using your medication. But, to be sure ask your pharmacist.

Well I called the pharmacist and he said I should have thrown it away after the end of May.

i might have checked with my doctor instead

it might be legitimately no good, on the other hand a pharmacist would tell you to throw it away, they want to sell you more