First - welcome to ASF bro. Great place for help.
Next... Chances are REALLY good you didn't
screw up your body bro relax. Did starting young have an effect? Yes but you're not screwed for life by any stretch of the imagination so don't stress out. You're still very young so you have PLENTY of time to make changes and grow in a healthy way. Don't sweat it. I started this stuff before you were born and I'm still here happy and healthy all these years later. Just start getting yourself on the right track now.
Like they said above, blood work will give you the exact state of your body. Once you are armed with that info then you can plan what's next. Don't have insurance? NO problem, Check out this thread and see how you can get the blood work on your own... cheap to.
JJ is also right, 2000 calories a day isn't going to get you growing. That's more of a maintenance amount of food. BUT of course the amount isn't the only part. You have to eat the right stuff... at the right time etc.
Lastly, you look young because you are young. Trust this old ass guy, there isn't a big difference in looks from 17 to 21. We spend half our life trying to look older and the rest trying to look younger. Don't sweat the small stuff bro.