I will post as someone who has been in your shoes and is just climbing out of hell now. Everyone here can give you advice, but I am someone that lived through this and ended up getting into University this year (at the age of 23)
I am UWOmang and this is my story.
I didn't do so well in high school and finished with an average of 64%, I always wanted to attend university and UWO was my number one choice as a kid. Well, I said "yeah right" to those dreams and ended up attending Fanshawe for business admin.
I dropped out, just like you at 19 and had nothing. I started looking into different programs and engineering seemed interesting to me so I started reading books on engineering and doing the math. I really enjoyed it and decided to pursue this dream. I didn't have good high school grades so applying to a university was not one of my options. So, I asked my girlfriend about what I could do about my marks. She recommended ILC. (http://www.ilc.org/landing.php)
At ILC I managed to get good marks and had a midterm mark of about 91% and started sending my marks to different universities. I applied to Queens engineering and UWO mathematics because both interested me and I decided to let fate decide where I went. Queens did not get my grades on time so they didn't look at them and I was rejected. UWO looked at them and realised that I could be admitted as a mature student, because I had been out of school for 4 years. I ended up being admitted to UWO without any conditions (I do not need to finish my ILC marks, but with them uncompleted I have an average of 82.5%) and I am attending in the fall.
What does this mean for you?
This year, you will be out of school for four years. Do some work at ILC, get your calculus, functions, physics, whatever and beef up your marks a little bit, apply as a mature student and I can guarantee you will get in.
My story may sound like I did not work hard. But I spent 4 years getting these marks up, working full time jobs and really dedicating myself to the goal of getting into University.