Here are some polished options depending on the tone you’d like:
Clear and direct:
“A month before my stroke, my body began warning me. These were the first symptoms.”
More reflective and emotional:
“Looking back, my body started sending warnings a month before my stroke. These were the earliest signs I didn’t recognize at the time.”
More formal:
“Approximately one month prior to my stroke, my body began to signal that something was wrong. These were the initial symptoms.”
If you’d like help expanding this into a paragraph, a narrative, or an educational message, I can do that too.