No, you cannot get chickenpox after having shingles, as both are caused by the same virus already present in your body. Your lingering pain is likely postherpetic neuralgia, which can be managed with medications like gabapentin, pregabalin, or acetaminophen. \n\nHowever, your new symptoms of high fever, headache, and painful black marks (which could indicate a secondary bacterial infection) are concerning and not typical three weeks after shingles. You should not self-medicate for these new symptoms. Please see a doctor immediately for an urgent evaluation to rule out complications like secondary infections or meningitis.