I would go see a hairstylist if I want to straighten my hair. There are different kinds of relaxers out there, but the problem is that it's for different types of hair, and some work different from others. If you try to do your own hair and you don't know what you're doing, you're not helping the situation any at all.
A professional hairstylist would know what's best for your type of hair. You most likely need a relaxer, and ask what products you need to use between appointments to better maintain your hair.