The five days start when a woman becomes niddah (or acts as though she is niddah, harchakot and all, because she is not sure about her niddah status). Abstention beforehand, even driven by halachic concerns, does not count toward the five days.

If we understand you correctly, your staining became a flow only on Tuesday after sunset, and at that point you told your husband that you were in niddah. In that case, your five days began on Tuesday-night/Wednesday, the halachic day on which you became niddah.

If a flow did not begin on Tuesday night, but you just had heavier staining on a colored undergarment, then it is possible that you never became niddah. When a woman tells her husband she is niddah out of a misunderstanding of the halacha, that can sometimes be reversible. If you are in doubt about what your status was on Tuesday night, please get back to us here (or, for a more immediate response, at our hotline) with details about what you saw.

Please write back with any further questions.