Search "CFA" across all forums, also pull-ups. Have you tried those? You have got to put the effort in on a daily basis. Install a pull-up bar at home and try every time you go through the door. Use the assisted pull-up machine at the gym. This is not a skill you can pull an all-nighter on. Presumably, you are already beating yourself up for not getting this in hand a year ago. Get your form and breathing right. Push though.
Edit: I do not intend to come across harshly. Someone your age in good health, regardless of gender, should be able to ramp up and do these.
Believe you can, blank your mind to discomfort, and think about how much you want to achieve your goal of attending USNA.
Many years ago, in the last century, I had to gain the ability to do push-ups and pull-ups, before I started my military career. Sit-ups and running were easy, because I had done them for years. I had only done "girl push-ups." Muscles screamed and protested, that evil inner voice whispered "I can't." I just set my mind to it, and I did it. I still do them, most mornings, to retain the strength and muscle memory. Sets of basic body-weight exercises. It has paid off over the years. I hoist the big bags of dog food over my shoulder and head to check out at PetsMart, heave bags of salt for our well into my cart at Sam's Club and take two bags of salt at a time down the basement stairs.
You CAN do them. Forget about your body type and other mental lint.
Have you consulted a coach at school? Grip strength could be your weakness. Good form is also key.
I am rooting for you. Feeling physically strong and capable is a great underpinning for lifetime confidence.