I had male parakeet 3 yrs.he eats puffs up slings his head all around a foul smelling slime and seeds come out?

first got he did it once month,he would just puff up for a little while.now he stays puff up all time but he still hoops around in and out of his cage eats good its just getting more frequent,sleeps alot.I have changed up the food.I've gave him gravel thinking the grit would help grind up the seeds.So please help if you? can Please,help?anybody know anything it might help???