Being an endo you'll probably put on mass easily, especially with carbs.
I personally eat more fats and less carbs, so when i gain it's as lean as i can make it.
Fats need to be healthy when possible, coconut milk and flaxseed are two good additions.
If i don't watch what i eat, the fat packs on very fast, my guess is you're the same.
As gmanall says, post up your stats, routine and diet.