New Onset of Post-op Discomfort

I underwent VSG on 1/24/19. I also had a large hiatal hernia repaired at the same time. I have been feeling much better in the last week or so, especially during the day. Other than being somewhat fatigued, I feel fine while I’m up and around. For the last 2-3 nights, though, I toss and turn with constant middle-back and side pain. It’s not a burning/stinging pain or anything. It’s more of a really strong ache. Reminds me of a “flu backache” for anyone familiar with that. It doesn’t matter which position I lie in, it’s constant. Has anyone else experienced this? What in the world is causing it? I have no other adverse symptoms at this point.