My advice to you would be looking into certs... I have been doing alot of self education and I believe certs will give you not only the proof that you know a topic but the feeling of completeness.
I am 23 I will be 24 this month on the 28th, I have been actively programming since I was 12 and I have been doing it for a living since before I graduated high school in 2010. I recently began taking courses at my local community college to bring up my GPA which was a 1.9 when I left due to some of the same reasons you didn't do so well. I lived to prove that you can be successful without a degree, my family told me I would never amount to anything without a college degree, and I am making around 125K in Detroit, MI where the median salary is 35K.
With all of that being said, just take the small steps in the right direction, I know I have and its a good feeling.
I hope this helps.