Jessica, it’s your son’s snacking pattern that is interfering with his meals, and that’s OK as long as his snacks are nutritious. The issue of him eating in his bedroom is a different situation. My first concern is why he’s spending so much time in his room. Most 3-year-olds want to be with others, especially their moms. My second concern is that you can’t control where he eats. If he’s helping himself to food, store it above his reach and insist that all food be eaten at the dining table.
If that fails, do what I did when my son starting taking food to his room: Tell him that if he eats in his room, “critters” will move in. He took that to mean bugs and stopped immediately!
Finally, what is mealtime like at your house? Is there chaos, noise and demands for attention from others? If so, your son may prefer solitude because it’s less stressful. You might also want to discuss your son’s denial of authority with his pediatrician. There may be other, non-food issues here. Good luck.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.