26/f. healthy. past 2 weeks body itching when overtired, not interrupting sleep. not everyday. also, sudden right knee pain. chances of lymphoma?

Quite low: Before you activate anxiety symptoms it is a good idea to check into the status of what you already know you have - thyroid issues. See you provider for eval of your levels. Meanwhile, try to avoid situational reasons for being overly tired and consider a knee support cuff. It's good you think of yourself as healthy, but do check thyroid levels and basis for knee pain w/ a provider ASAP. Best!