Agree with Mandolen, it sounds like possible gastroparesis to me as well. I had nearly identical symptoms for a couple of weeks last year and was found to have temporary gastroparesis (mine luckily only lasted a couple of weeks then returned to normal). We were trying to figure out if I had Crohn's, and I had the capsule endoscopy done at the time. The pillcam stayed in my stomach for the entire 7 hours (normal time in the stomach is 20minutes)! There was still food in my stomach from a couple days before!
An upper endoscopy and/or gastric emptying scan is probably needed to test you out.