This is where an "Apprentice Training Logbook" would have helped. You record your hours in the book and work you did, then get your boss to sign it on a monthly basis.
Some information:
http://www.cnc.bc.ca/apprenticetoolkit/record.htm A sample of what the book should contain:
http://www.cnc.bc.ca/apprenticetoolkit/pdf/recordbook.pdf Hope this helps.