Why is my fish acting different and have a whitish film on his head?

I have a goldfish in a 1 gallon tank. Last week he would open and close his top fin and he looked happy, but this week he has his fin closed on his head and keeps swimming around sporadically. It also looks like there is whitish slime on the top of his head. Is he sick what should I do? Also before he would always hang out towards the bottom of his tank and now he is always at the top. How can I help him?