Do you have a partner, family member, or close friend that could sort your mail first? You used the word flat and I'm not educated with the NHS. In the U.S, our doctors send out letter reminders for appointments, explanation of insurance benefits, bills, and test results. Idk if it's only test results with the NHS. But having someone look and explain "Oh this pile is about __" might help lessen your fears. I'm sorry about your health condition.