Will this impact my application under CEC though?? They only ask for you to send in your most recent T4 and notice of assessment, which i have.
And as far as CRA, what can they penalize me with if I didn't actually owe them any money?
You would probably be OK with CIC with the most recent tax year. If they really wanted to investigate, tho, they would clearly know how long you've been in Canada and see that you did not file for those years.
And, are you REALLY sure you didn't owe? For example, you have to file if: "You have to contribute to the Canada Pension Plan (CPP). This can apply if, for 2010, the total of your net self-employment income and pensionable employment income is more than $3,500." I realize students often do not make much, but most make more than that... Also, keep in mind that Canada taxes on GLOBAL income if you are residing in Canada. Still, as already noted, more likely you missed out on benefits.
In any case, you can file back taxes - if you didn't owe, there wouldn't be penalties.
http://www.cra-arc.gc.ca/formspubs/t1gnrl/llyrs-eng.html