White spots on throat

So I had white spots along with some swelling on my tonsils a little over a week ago and got tested negative for mono and strep as well as covid. I was put on steroids and it went away and as soon as I finished the steroids it came back. I don’t have any pain or discomfort. I only have really dry mouth in the morning with some swelling and my doctor told me to change my diet and maybe it’ll go away. Idk If I should be worried or not.