As Moldy stated keep copies of everything sent to you as well as what you send them including the envelopes. Further, get an accordian folder just for this. Start a log, in it record date, time, activity ( phone call, Dr. appt, medical procedure ect...) who you talked to & what was said. If traveling to appiontment mileage & time & who made or requested the appiontment. Prescriptions by name, dose, Dr who prescribed date prescribed & why.
Keep notes of every discussion related to this from your employer, Dr., insurance, ect...
Write down what you tell anyone involved & do not change what you say or assume everyone involved knows your story. Do not paraphrase or use different words in your descriptions.
I know this sounds unnecessary & overkill. However, I speak from experience & just changing how you describe what happened, how you feel, ect....by one word can costs you everything.
Remember, insurance companies do not like to spend money. They will check every report from every source to find any descrepencies so they don't have to pay. Although this maybe short term your memory will not be completely accurate in 6 months. Stay on top of this & you'll be fine.
Oh yeah make sure anyone in your family or friends knows your narrative. What they say in passing to your employer, Dr., ect... can be used against you as well.
Good luck.