CHICAGO — Jackie Kramer thought she had COVID-19 late last month. Everyone in her family tested positive. And she had symptoms: congestion, a headache and fatigue. Yet the Andersonville woman kept testing negative, over and over again. She took several PCR tests and rapid, at-home COVID-19 tests every day for a week. “I don’t understand why I tested negative for a week when I had all the symptoms,” said Kramer, 56. “I’d stare at it, like, how can this be?” She spent the week isolating from her husband, 21-year-old daughter and 18-year-old son, to avoid catching COVID-19, just in case the tests…