daily nausea and uneasy feeling in stomach area

For the last three weeks, I have had intermittent nausea daily. I have IBS-C. I take Linzess every day and that helps me go every day. The last three weeks, however have been total hell. One minute I can eat and the next I feel like throwing up. I haven't thrown up, but the nausea comes in waves.
I was in the ER for the nausea over night and they could find no problem on the Two CT scans they did. I am going to have an endoscopy soon to see if my stomach is delaying emptying. I am going out of my mind wondering what is going on. Could it be a long lasting flair of IBS C. I can't afford to lose weight, but when I can't eat, I drop a pound or so. I am so afraid that it is Gastroparesis. To treat that is very serious medications that can cause other problems. I know I have to weight to see what the endoscopy says, but it is torture waiting especially when you get these waves of nausea. Could IBS-C act the way it is now. When I first got IBS-C, I had same symptoms, but only for a day or two. I would appreciate any insight.