I have the same problem, haha. I write fanfiction and original work, so my vocabulary should be at least above average. However, whenever I write I seem to keep using the same words over and over. Most of the time I tend to read novels and other fanficiton works to find some new words to use.I feel my vocabulary is too small for a writer. :/ I'd say it's not too small in general, but not really big or anything either. I should learn some new words sometime. Or buy a dictionary and thesaurus. Either or. :p