First, you need to decide what you want: payment, credit, removal, or penalties for the person stealing your images.
Take screenshots and save PDFs of the website where your images are being used. Save them along with the date for future reference.
Canadian law is very clear that you own the copyright to your images, BUT it does depend where you have shared them (i.e., some image hosts require you to blanket release your copyright to them to post your images there.)
So next steps will be determined by:
- what you want
- what evidence/sharing protocol you have through external services or listed on your own website.
If the blogger is in the U.S., you could explore the DMCA:
Ways this might work in Canada: