I would have probably been that girlfriend suggesting to get all the child support possible, but I'm also that girlfriend who would LISTEN to you and offer you options that - in my opinion - worked.
Guess what? You can go to a lawyer and explore your options. Can't you apply for child support up until the time your son turns 18? Like a few months before that? And can't you go after THE ENTIRE amount? You might be able to, you just have to talk to a lawyer. It would be hard to take away a 17-year-old, you know.
You're one brave woman. I wish young women were focused on getting education and careers first, children - second. No judgement! Just saying: you deserved to make much more than $9-10 per hour.