It is possible you picked up a bug while on MC. The presence of yellow phlegm does indicate an infection. Yet, most of us who have fasted or done other cleanses have also experienced flu or cold like symptoms as excess mucus and toxins are eliminated. The important thing is that you are doing better. Its really impossible for a lay person to give an exact answer, even a medical professional might have to guess unless he did specific tests for bacteria or viruses. My guess is you might have had some of both (detox and illness) which would explain the rather extreme symptoms you encountered.