Preposition in this sentence ? my mother is ill fever.

I believe there are no prepositions in this sentence, here is an example of a few prepositional words:

about below excepting off toward above beneath for on under across beside(s) from onto underneath after between in out until against beyond in front of outside up along but inside over upon among by in spite of past up to around concerning instead of regarding with at despite into since within because of down like through without before during near throughout with regard to behind except of

There are no Prepositions in this sentence. But here are a few examples:
About 
By 
but 
of
at
hope this helps