Welcome to PC nathaniel1993 and so sorry this is happening to your brother. This must be so confusing and scary for you. Do you mind me asking if you're male of female - maybe I missed this is your post? Is there any history of mental illness in your family? Sometimes a mental illness can set in late teens and early 20's - for example my own deceased brother developed Bipolar and revealed his sexual orientation in his mid 20's - he went through a big personalty change. Has your brother done any drugs like synthetic marijuana or bath salts? - these legal substances have been known to produce psychotic episodes.

I think you need to have a talk with your brother and ask him what's happening/to explain this behavior. Ask him where he's getting this sedative and why he's lost interest in school. Since he's been inappropriate in your bed, I feel you need to put a lock on your door - mainly because of what you found on his computer. This is your place so you have the right to boundaries. Explain you're worried and need some answers. I sure hope he sees a doctor and you should go with him.