Its good to know that you are aware about your strengths and development areas. While you say that you are not good with sciences, is there any other career option that you have thought about apart from polytechnique or ITI?
There are various other options like commerce,management,mass media that you can consider. You can by all means get in to technical fields but before doing that atleast read up more on various careers on http://www.youngbuzz.com/careers/career-options
If required give the career test which will be very helpful in understanding your aptitudes,interests and personality which will help you make a wiser career decision.
You can read up more on the career test on