My dad has PTSD, OCD and not sure what to do. Any help?

He is only 70 years old. We are just having a time with him. We don't know were to go to get help..ER? He sleeps all the time..He goes from not eating to way overeating, some days he wakes up frantic. He does not know why he is frantic, he worries, asks questions over and over, he recently started walking around naked.This is really not good. I have teenagers and young children that come over...I don't know what to do.