A little late to the party but ..... better late the never.
Druiztx - started to hit on this. fjocheese - let me as you something. And fair warning, you may not like what you hear. But hey, the truth can hurt.
You say you that "math really does come easy to" you. What level math courses are you taking? Have you taken any calculus courses yet? If so, were they honors, AP, or college equivalent? You may have taken a couple algebra classes, geometry, trigonometry, and some pre-calc courses; but if that's as far as you've gotten, I really do not think it'd be fair to assume that math would come easy. Trust me, once you hit AP (or equivalent level) calc, you will see the difference in the degree of difficulty. Everyone hits a wall at some point; you simply may have not gotten there yet.
Make no mistake, I am in no way questioning your math abilities, or claiming that you are not good at math. And you may very well go through a large portion of math classes in your engineering program and not break a sweat (props to you if you can; but believe me, not that many people can) I'm merely saying that, unless you've taken AP calc and more advanced classes -- don't count your chickens before they hatch.
Subpoint: regarding engineering/"being good at math." Here's another question for you. Should your Military plans go south (for whatever reason), what do you plan to do with your engineering degree? Any ideas yet? I'll tell you one thing that I see EVERY year with this. A lot of kids come in with the mindset of getting a degree in engineering. Why? Like you, they are good in math and the sciences .... HOWEVER the big kicker and pattern I began to notice very early on is that, a lot of folks don't know what they want to do. And I don't blame them, it's hard to make life decisions at such a young age and with practically no experience. The point I'm trying to make is that, if you have some sort of an idea (doesn't have to be set in stone, but just a concrete idea) - it helps slugging through engineering so much easier. Because if you have an end goal in sight, it helps keep you focused and driven towards that end state. A lot of kids come in being "good" in math/science; then they hit college level academics. Find out that it's actually tougher than they thought it would be. What do they do? Switch to underwater basket weaving. Why - because the lack that end goal; something to hold onto when things get tough. Case and point: in my battalion, in my class specifically, we probably started out with 1/3 out of 60'ish + contracted cadets who started out engineering ... less than 5 of us remain today (that whole "look to your left, look to your right" spiel is 100% accurate) I'm fairly confident, that if I didn't have something to look forward to, I would have dropped engineering 3 years ago.
You also say that you are "very diligent in your school work." We'll see, come your freshman year. I'm sure if you do enough lurking, you will see the shear amount of posts from parents, freshman cadets/midshipmen and their respective upperclassmen counterpart, they will all tell you that what you in high school SHOULD NOT be paralleled to your experiences in college.
College is a very very different place; with a whole different set of dynamics. In high school, you had to go to classes all day long. Then afterwards, you played a sport (or something to that degree). And after a grueling day out in the classroom and on the fields, you go home and grab a bit to eat and do homework.
And then there's college; where you (technically) don't have to go to class. You literally make up your own schedule; there's no one there to tell you when to go to sleep and when to do your homework. That's all on you to decide - whether you want to prosper and succeed or flounder and fail. ... and on top of that, there will be PLENTY of distractions to keep you busy in between. Friends, socials, clubs, girls, and perhaps some other things that shouldn't be done underage. And that's where time management comes in. It will be up to YOU and you alone to decide when to do what.
I'm sure there are many students here who will agree of me, that there is a very tried and true triangle of life in college. There are 3 things in college you should be aware of: sleep, grades, social life. You can ONLY choose 2. .... tread carefully.
And now lets look at your schedule. Engineering. ROTC. Football. .... that's a lot of time my friend. My point is, you are at a pinnacle in your life right now. You've got a lot of awesome plans in mind. The only problem is, you probably don't have enough time to do them all. In a perfect world, it's possible. But unfortunately that's not the world we live in. You'll find that out real fast in the Military.
And I get it, believe me I do. I was once in your shoes a few years back. That feeling of being a senior, and about to step off into another chapter in your life - and the Military being one of it. No greater feeling right? Unfortunately for you, you are now at a crossroad. Unlike most of your peers who could probably just make it up as they go, you probably will not have that luxury - being in the precarious predicament you are. If I were you, I'd spend the rest of the school year and summer before freshman year of college to sit down and figure out what you truly want to do in life. In 5, 10 years down the road - what do you envision doing? What do you want to do? It's not going to be easy - especially being 17, 18 years old trying to make big decisions such as these and with the very little real world, practical experience that most don't get without age and time.
There are plenty of folks here on this forum who would probably be more than happy to throw some advice your way. I would not be where I am today without some of these people.
.... that was a pretty substantial post. But if you made it all the way to this point, you'll be in good hands.
Knowledge is power my friend.
Best of luck.