Don't worry, the process takes longer than you expected.
Here is what you can do:
1. Call Canada Revenue to find out the progress. (The best way and quickest way to find out).
2. Wait longer, they will difinitely send you an assesment letter no matter whether they will return you the tax or not.
If they told you they would refund you, they usually will.
ps: They will also send you a letter telling you about the GST refund. About $400 a year for a low income person.
If you claimed wrong or you disagree their assesment, you can always reclaim it.
如果今年他没有给我退税的话, and you agree it, you can not claim it next year.
Hope it is helpful.