It means that you are going to the bathroom or toilet for a short time. Introcuing a time reference suggests that there may be a reason for it not normally associated with the act, such as being upset and wanting to be alone.
The problem with your original sentence is that it is taken out of context. It could very easily refer to a repeated action, for example:
Every morning I get up at seven, do a few exercises, then I go to the washroom for a while. After that, I get dressed...
Again, "Do you ever see a ghost?" would refer to a repeated action:
"I often go to that old house on the hill, the one they say is haunted."
"Really? Do you ever see a ghost?"
The question "Have you ever seen a ghost?" is in the present perfect. The present perfect is used to link an action in the past with the present. In this case, it means: "Do you have experience of ghosts?"
"Welcome to Weird Science, the chat show featuring mad scientists. This evening, we welcome Professor van Tomm, who has been conducting studies into ghosts, phantoms and spectres. So tell me, Professor, have you ever seen a ghost?"
"Go to sleep" is neither present simple nor present progressive: it's an imperative -- that is, a command. "Go" is not a finite verb at all, but the basic form. You can't normally see that it's the basic form in English, except when you use the verb "to be": "Be good", or "Be careful", for example. So here, the verb doesn't really have a tense at all.
You can say either "it refers" or "it is referring". I think the simple present would be more usual here, because that sentence refers to the same thing every time you write it or read it in that context -> repeated action. But the present progressive is also OK.