Taking a course of antibiotics can influence the health of the liver and immune system due to the actions of these medications on suppressing these systems. In the recovery stage after illness (convalescence) the body may take some time to rebuild these systems and in the meantime blood is shunted from other areas of the body to help these systems to recover. This means that you may be left feeling lethargic. It is recommended that you ensure that you receive enough rest to improve immunity and not cause a further weakening of an already degraded system. The sleep deprivation you are currently experiencing should be short lived and recorrected once your body gets back on track again.