Before diving into reapplication, take some time to reflect on what might have held you back. You may be able to get feedback from admissions, but it could simply entail you taking stock: was it academic or leadership or athletic or some combination where you fell short.
Then set about rectifying that. And make sure you take a plebe-like schedule wherever you go to college, e.g. calculus, chemistry, English at freshman level or better. Build good relationships with your professors. Get involved in ROTC if the school offers it.