I'm now 30 and work for a major SV website. I am a bit older than most of my colleagues, but I keep up just fine. Like you, I wish I had gotten that CS degree as well, but you only let your mistakes defeat you when you stop trying.
Now, before everyone starts freaking out, the trick this whole situation is that you must be willing to learn how to do everything the right way. No cutting corners, no copy pasta. Treat this like a magical classroom lab where they actually pay you.
You will feel stress. You will work harder than you've ever worked. I was putting in probably 100 hours a week between my day job and this work. But I also got to a point where I could really write code and archetect software in about 2 years time.
It really helps have a close friend who you can turn to when you need someone to help guide you a bit, but if you don't have one, try to get ingrained in some dev forums.