Thrush wont go away?

Hello, so 2 weeks ago I took my bn do the dr and was diagnose with thrush. De gave him medicine which I been giving 4 times a day. However the thrush is not going away :(. I keep cleaning the inside of his mouth regularly, sterilize paci and all toys and bottles. He is mostly breastfeed with 1 bottle of formula during the day. Any other remedies? How long is this thing supposed to last?