Get in the habit of using spell check. It's a good thing because you can see what is misspelled and learn from it.
Even in my middle age, I occasionally use it when something I've written doesn't look quite right.
It will serve you well in life, not to appease the grammar Nazi's but to become a well rounded and more intelligent sounding young man.
The difference it makes in one's perception of another is amazing.
I've always spelled pretty well. That came from reading books, magazines etc, also a good learning experience, really helps to improve your vocabulary.