Worrying about weight when you're overweight is fine, but excessive worrying isn't. Ask yourself whether you're doing something to be healthy or whether you're doing something to be thin. The first is fine, the second is not.
Veganism is also no excuse for eating junkfood and desserts. How do you think vegan monks in East-Asia were fit enough to practise their martial arts all these centuries? They certainly didn't have access to junkfood.
As for healthy diets:
I don't know if you still eat eggs or not, but if you do, you could make two-ingredient banana pancakes for breakfast (just Google for the recipe). If you don't eat eggs, then just eat the banana and add an apple too. Or eat two different types of fruits instead.
Then for lunch, have a pasta salad. Throw in some tofu for protein, if you like.
For dinner, rice (or potato, if you prefer that) and beans (for protein), and then some other vegetables (the more variety of different types you include, the better).