7 weeks post tonsillectomy - constant coated tongue

I had my tonsils out appoximately 7 weeks ago. Since then, I have had a coated tongue. Especially right at the back. I am fairly sure it isn't a thrush infection from the post procedure antibiotics (I've tried oral thrush drops and probiotics etc).

Has anyone els had this? Is there something about the procedure itself that could be causing it?