No. Please don't wait until Monday. And, this does sound like a GI issue. And, I would go to the ER. This time it will be different as you are not going in for what you think is an MS thing. You are going in with symptoms of a serious illness - nausea, constipation, gray stools, etc. This needs to be checked out as soon as possible, please. Explain to them the symptoms you have been experiencing such as the nausea, chest pains, vomiting, stool color, etc. They'll do blood work there and possibly radiological tests to see what is going on. If you wait for the dr., either it will take a while to get the tests scheduled and the results in or, as the dr. should, he'll just send you to the ER.