When a woman says she thinks she is in niddah, but she does so out of halachic misunderstanding (or lack of information), it does not make her niddah. In general, it is best to say you are concerned you might be entering niddah. But in this situation (and cases like it), your statement did not make you niddah.

That leaves us with the question of what you saw on the toilet paper and under what conditions. The status of staining on toilet paper is subject to halachic debate and depends on several factors. Please read our site's article "Toilet Paper" and get back to us with more information or questions.