[hackermailman]

Go to expii.com and start doing a module to test where you're at. You do exercises and if you don't get something, it shows you a 5min lesson. It's a startup by the guy who coaches the US olympiad team. When you're done find some introductory text that goes about proving things, such as Hoffman & Kunze Linear Algebra or Concrete Math by Knuth et all. Concrete Math is accessible to a motivated highschool student. You have Math stackexchange to ask questions or hire a tutor from a local university to walk you through some of the proofs at a coffee shop on a Sunday afternoon. I paid a grad student to review my terrible attempts at proofs when I started going through the exercises of these intro books, highly recommend you do this too.