When should I go to the ER if I think I am having a gallbladder attack?

On Thursday afternoon I began having pain on my right side right at the bottom of my rib cage. A dull achey pain has been constant there since with sharp pains coming and going. I have been feeling nausea and some pain/almost burning in my chest more on the right side. I have a horrible headache that started about two hours ago. The pain is worse at night and after eating. I haven't eaten much as I have gotten over the pain and don't want to do anything to make it worse. I have had diarrhea immediately after eating for a few months until this attack started and now I feel constipated. My temp is now 99.2 and is normally 97.6. I plan on going to the Dr. on Tuesday because of the holiday Monday, but I have heard horror stories of people waiting too late to go to get help.....