I have 3 weeks nausea, dihherea, and now fever with chills headache body ache. dr found nothing last week. history of crohns and immunosuppression?

Body ache : It is possible being that your on immunosuppressive treatment you can aquire infections faster. It's possible you have a viral gastroenteritis, but if symptoms are not improving with hydration, OTC remedies, it's possible you may have a bacterial process and need antibiotics. See your doctor again for evaluation, and obtain some basic labs, CBC with differential and BMP.