Uterine bleeding makes a woman niddah. This is the case even when the bleeding is not a real period. A woman in niddah is required to wait the five days (where day one is the day she becomes niddah), perform a hefsek taharah no earlier than day five, and count seven clean days. So you will have to go through the full process, even though this flow began so soon after immersion.

Spotting or irregular bleeding are very common as the body adjusts to weaning. You may find it helpful to review our site's articles on stains, "Ketamim" and "Toilet Paper" for information about related halachot. You may also wish to consult with your physician at this stage about the possibility of switching to a combined estrogen-progesterone pill, which is often associated with less staining.

Please write back with any further questions.