I Have Been Vomiting A Dark Brown Liquid For Several

I have been vomiting a dark brown liquid for several hours now. I do take Percocet for chronic pain. I had RnY gastric bypass surgery 4 years ago and after that surgery, I have not vomited like a "normal" person would. This is the first time that I have actually vomited like this. I ate at approximately 11 am - 12 pm today and it is now 9:30 pm. That was the last meal that I had. Could this be an opioid overdose? Should I go to the emergency department?