Neither muscle nor fat accumulate overnight. Its also difficult to gain muscle without gaining some fat. Increase your intake and keep track of your weight and bodyfat%. If the weight you’re adding has a muscle/fat ratio that doesn’t increase your bodyfat% much, you’re probably not eating too much. If you’re the weight you’re gaining has a muscle/fat ratio that increases your bodyfat%, you should probably cut back until you reach a more appropriate level.