That clearly shows that you don't know what "theory" means in science. In everyday useage, "theory" might mean something one is not sure of. But in Science, a theory is an explanation for observed facts. In fact theory is the highest formulation of an idea. In science, something becomes a theory only when sufficient understanding about the subject is obtained. To be a theory, there has to be an explanation of facts, and a demonstrable mechanism.
Creationism is by no means a theory. It needs a lot of work to make that a theory. Data should be collected, viable mechanisms should be proposed, each mechanism should be investigated, and once a complete understanding of the phenomenon is arrived at, THEN it will be a theory in the scientific sense. Just saying "god did it, end of story" does not make a theory, it just makes a (very short) story.
In short, in Science, if something is a theory, that means we know almost everything about it. You share a common misunderstanding, and so scientists have taken great pains to explain this point.
Evolution, like gravitation, is both theory and fact. There are facts of evolution, and then there is a theory to explain the facts. The facts of evolution are the clearly evidenced change of organisms. The theory is very complex. One theory was proposed by Darwin, and he also gave a mechanism (natural selection), but today the theory has been refined a lot, and the mechanism is understood more in terms of genetics. But the facts are the same. Go through this link to understand why something has to be BOTH a theory and a fact, not one or the other.
Evolution as fact and theory - Wikipedia, the free encyclopedia
The best explanation for laypersons was provided by Stephen Jay Gould: