The online tool, normally found here: http://www.cic.gc.ca/english/citizenship/rules/index.asp, is being updated, due to changes brought about by Bill C-24. As the child of Canadian-born parents, you are a Canadian citizen, at least as of 2009. All you need to do is to apply for proof of citizenship as described above.
The only reason I can think of to determine whether you were a citizen before 2009 is if you have children who may have inherited Canadian citizenship from you. As of 2009, it is not possible to pass citizenship to a child born abroad in the second generation. If this is your concern, you can have a search made of citizenship records for a $75 fee:
http://www.cic.gc.ca/english/information/applications/guides/CIT0058ETOC.asp
If you apply for proof of citizenship ($75) AND a search of records at the same time, you do not have to pay an additional $75 for the search.