Exhaustion with stomach virus--normal?

I have been struggling with a stomach virus for about 5 days now.  For the first 3 days or so I hardly ate at all and had diarrhea several times during those days.  Diarrhea finally stopped yesterday, but my stomach is still a little iffy.  I am still not eating much compared to my pre-illness state.  My concern is being fatigued.  I became weak during the first few days of diarrhea and little food, but am continuing to be very tired, like I don't want to get up and do anything.  Is this level of tiredness normal?  The doctor suggested that being dehydrated and not eating enough would contribute to being weak, but I'm wondering how long of a recuperation is normal now that I do not appear to be dehydrated anymore.  I'm starting to get a little worried!