Freedom in Kant's Ethics?

In one of my other classes, Introduction to Ethics, we discuss several different moral theories and ideas. Since ethics is a very interesting philosophical subject, (and I won’t lie, since I need to finish 12 blogs ASAP and I need some material to work with) I will share some of what I have learned. The first major ethical theory we learned about is from Immanuel Kant.
Kant proposes that rationality must be our basis of ethical conduct. He suggests that we may exist transcendentally solely through our ability to reason. That is, our reason may exist in and of itself independent of outer influences. Also, according to his philosophy, we can freely control our rationality but we cannot control our desires. Furthermore, he supposes that every human being is rational, or capable of rationality. He also says that rational beings are ends in themselves, and that we must realize that other people are ends in themselves as well, and treat them accordingly. So, he developed a categorical imperative – the law that suggests that a person should do that maxim which he could rationally make a universal law. He proclaims that his categorical imperative is an applicable universal objective law of morality.

Kant then suggests that we are most free when we submit to universal objective laws of morality. I find this a bit paradoxical. He explains that if we submit to our sensible desires, we are merely being influenced by outer causes in the phenomenal world. On the other hand, he proposes that if we rationally lead ourselves noumenally through rational submission to universal laws, we are indeed free. This is troubling to me because I feel that it begs the question, "why can't we freely choose to satisfy our drives and desires instead of reason." Perhaps our only freedom abides in our ability to choose what we submit to - desire or reason.