Should I go to the ER or stick it out till Monday?

I woke up early Thursday morning with severe pain in my entire abdomen. The pain was so bad that I couldn’t walk or stand up right, I had to bend over. I went to a walk-in clinic and the doctor there gave me an anti-spasmodic to help with bowel cramping. On Friday I felt better. The pain was still there, but kind of ‘masked’ by the medication. Once the medication wore off, the pain would come back. Today the pain is worse than Friday, yet still not as bad as Thursday since I’m still taking the medication. However I’m noticing that the pain is only in my right side now. I feel a lot of pain in the upper right quadrant, but if I press on the lower right quadrant it really hurts too. I have been taking GasX but it doesn’t seem to help at all; also I’m going to the bathroom normally. It’s Saturday and all the walk-in clinics with an X-ray department are closed.. I’d have to go to the ER if I really want them to investigate. Basically I’m wondering, do you think I should go to the ER today? Or should I stick it out and wait until Monday and see my doctor?