I have schizophrenia and most of the hallucinations I've experienced have been auditory (i.e. voices). I've had some visual ones, but not many.
The first one you describe doesn't sound like a hallucination. It sounds more like something you thought about then had a visual of in your head. Remember speech class? You calm yourself so you think that everybody's in their undees Then you look at everybody and imagine they're all in their undees.
The second one sounds like it could be a hypnopompic hallucination, which is a hallucination that occurs when you wake up from sleeping. They can happen sometimes to normal people, but happen frequently to people who have narcolepsy.
From what you said, I don't think you need to run to the pharmacy to get some Zyprexa or Seroquel. I'm not a doctor...I'm just calling it as I see it based on what I know. If you continue to have problems or concerns you should go to your psychiatrist, as he or she is the one who can give you the best medical advice.
Hey! Im going through the exact same thing rn! its been sometime since you posted this question and I wanted to know if you had any updates?!