What could cause temporary memory loss, weight loss, and constant diarrhea?

Hello doctor,

My dad has had constant diarrhea for a while. He cannot digest anything without it going right through him. He has lost around 60 pounds because of this in a little less than two months. He is confused quite a bit, and he cannot remember where he slept last night or woke up this morning. This has happened multiple times. He has Tourettes, ADHD, bipolar disorder, insanely high blood pressure, and is agitated all the time. He has a history of alcohol and drug abuse, sometimes while on medications. Recently, he had an ultrasound done, and they found sores inside his stomach, which have been left untreated. It is obvious that he is not healthy, but what could be causing these recent confusion moments or temporary loss of memory? These all happened after he quit his medications all at once. Please help.