Inflammation can slow gastric emptying. Have you had an endoscopy recently? It's possible there is inflammation in your stomach or duodenum that is causing this.
If there is no inflammation, I'd look into gastroparesis, delayed gastric emptying. Typically, a gastric emptying test is done to see how fast food leaves the stomach. If more than 10% of the meal is left after 4 hours, then you have gastroparesis. It's a fairly easy test.
Motility medications can speed up gastric emptying. There are also diet changes that can help - eating small, low fat and low fiber meals.
The typical symptoms of gastroparesis are nausea with meals, feeling full after only a few bites, abdominal pain after meals, vomiting, weight loss etc.