There is a halachic debate about a woman keeping onah beinonit during the first two years after childbirth. Most halachic authorities, including the halachic supervisor of this website, rule that today once a nursing woman has resumed menstruating, she goes back to keeping all halachot, and observes all three vesatot. You might want to check with your rabbi to find out if his opinion differs on this matter.

Note that veset days are only counted from a blood flow. If a woman using progesterone-only contraception experiences only staining, she would not calculate veset days from that staining, even if the staining makes her niddah.