Awww, sweetie, I understand. Back injuries are hard, because it is not like you have a cast or crutches as visible proof! Next time, as the doc if he/she can give you a note to show your boss - a standard "No Bending/Lifting/twisting for X days" would be sufficient! You boss may have dealt with employees before who have had drug issues, so now expects that from young people, but you are not them, and we know that. Maybe Clover will sleep pressed up against your back tonight - a doggie heating pad - and that will help it heal! Fur nurses are the best.

If you boss continues with those comments, consider documenting them, and writing a letter to his boss. It is sounding like harassment if he continues it!