Part of OCD I guess. The more intelligent u r the more you analyze things sometimes overanalyzing. Kahlil Gibran said "Our anxiety does not come from thinking about the future, but from wanting to control it." You feel that the earlier your detect your illness the more chances for you to get treated but having anxiety makes u focus on the worst case scenario & so you feel more anxious! Sometimes you may also feel that maybe if I take this lightly i will become more sick.