Regular intense cardiovascular exercise is great. Having had over half a dozen concussions myself, the increased cerebral perfusion it affords makes a marked difference in recovery trajectory.

That said, obtaining medical clearance first is always best.

Sleep, healthy diet, exercise, and low amounts of bad stress will pay dividends. Since you're turning 18 soon, try to avoid heavy alcohol consumption at least until you're feeling better.

You want good stress—be it mental or physical—the kind that lets you push yourself in a way that builds you up such that you can claw your way back to function and feel good doing it. Avoid the bad kind that tears you down and degrades function. Sometimes, no stress is best.

A psychiatrist could potentially work wonders for you, especially if they have experience with brain injury. They're experts in psychopharmacology, and their armamentarium includes a lot more than caffeine pills.

You're still young, so you have a lot more time than you think to heal and still live the life you want. Best of luck!