The words "normal" or "always" have no meaning when it comes to answering this question.
Any large meal will make most anyone feel sluggish as our bodies divert energy to digestion.
If you're insulin resistant (likely at your size even if you weren't born that way) than any meal heavy in carbs/protein will make you feel sluggish.
You'll have to experiment to determine what might reduce this but my guess would be if you lowered your carb intake and increased your protein/fat intake this would be helpful to your energy levels. (There would be a brief period of adjustment where you would probably feel a little less energy)
John is right on here. There are two things that can definitely make you feel sleepy:
1) a heavy meal. Your body has to divert energy to digestion instead of to your brain like John said.
2) a spike in blood sugar followed by a crash. This can happen to someone who is metabolically perfect - but if you add in any metabolic issues, this can be more acute.
My advice is to start eating smaller meals more often, and be concerned about the glycemic impact (watch carbs, make sure you always include protein and healthy fats). See if that makes you feel better. If not, I'd start by eliminating potential allergen food and slowly adding them back in.
Just to clarify my point on insulin. Carbs + protein spikes insulin. Fats somewhat off set this. Lowering the carb intake significantly and increasing the fat content would be a good experiment to see how it makes you feel.
I think the type of carbs matters. A typical lunch for me is a very large salad with romaine lettuce, spinach, bell peppers, tomatoes, and a half cup or more of lentils, along with my homemade sesame soy dressing. I follow it with a bowl of blueberries. It's all carbs, yet I feel very energetic after a meal like this.
