I took simvastatin about a year ago and took myself off it becaus...

From what I have read about these medications for high cholesterol, well the side effects you are getting aren't good ones. I think you should call your doctor and let him/her know what is going on and ask too be put on another medication that may work better for you as soon as you can.
I am not telling you what too do, I am not a doctor, but if I was having those side effects I would stop the medication until you can get intouch with your doctor on Monday. (some medications you have to wean off of, but this is not one of them.)
Too confirm whether you should do this or not, you can always call your pharmacist. I did that once and they told me too get off the medication that I was on immediately. It was a week-end and I couldn't get intouch with my doctor until Monday.
I hope this helps you out and another medication works better for you.
Good Luck, Sandy