ROTC is my plan B, and I'll definitely reapply.ROTC is another viable option. I knew a couple guys who did a semester or two at a regular college with and without ROTC before going to the Academy. One of the big things is to never give up. Even if you don't get accepted the first time, keep trying. Go to college to build yourself up and make you more competitive. As far as going the enlisted route, I also advise against that if your goal is to be a commissioned officer. One, there's no promise of you getting picked up for a commissioning program. I've seen several top sailors in my squadron apply for them and only one or two got accepted. Two, you won't be able to apply right away so while you still get to serve your country, your window to apply keeps shrinking.
I second the Summer Seminar program. I did it myself and was a detailer for it, well worth checking out and it's almost a "prescreen" for potential candidates. It's not the end of the world if you didn't go either, so don't worry about it. Are there any areas where you may think you are weak?
As far as weaknesses, my only real weakness is the fact that math is not my strongest subject at all, which I know is bad since USNA is all about STEM...