I've had mid-back pain and upper middle and left abdominal pain that has been very bad at night for the past week. I haven't had much sleep or restful sleep. My chest feels tight, also. Should I go to the ER or wait to be seen on Monday?

Go to the ER. What you describe could be a pancreatitis, a colitis, and esophagitis with severe heartburn. This could also be an ulcer. As your abdominal pain is on the left side, it is less likely but still possible to be a gallbladder problem. As it is worse at night a hiatal hernia with gastritis and acid reflux or an ulcer are more likely. It is time to get a diagnosis.
Tomorrow. It sounds like your symptoms have been stable for about a week. Your family doctor knows you better and is best suited to care for you. Use symptomatic treatment and follow up tomorrow. Only if you are worse go to the ER.
If pain is worse, ER. If the pain is about the same as it has been for the past week, then prob tomorrow would be fine. But if it is changing, worsening, or new symptoms, then I would suggest the ER today.

Related Questions

What could cause upper abdominal pain and mid back pain? I've been on a picc line for antibiotics to cure a staph infection for the past 5 weeks.

Get examined for. Stomach, gallbladder, liver, spleen, kidney, and intestinal inflammation or infection. Take care! Read more...
Many possibilities. The recent staph infection may or may not be related to your current abdominal symptoms. Ask for an ultrasound of your gallbladder, to look for gallstones when you get in with your primary. Good luck. Read more...