I think I have trouble learning things now, any idea why or how to help?

Your 17 and don't drink or smoke, your grades are excellent, there are always going to be people with better grades. Keep active, for now just do the best you can if your good at many things you will find your calling in life in a few years, for now make sure you get plenty of exercise and time spent away from books, they will always be there. It's more important to keep healthy as soon you'll be more able to use all the great things you already have learned. There are thousands of people who have done great things with no education at all. Hang in.