Why does clear thick mucus sometimes come out during withdrawal bleed while on triphasic pill? (like ortho tri cyclen (ethinyl estradiol and norgestimate) lo)

Light menses?: Women on hormonal contraception generally have relatively light menses. Also, the healthy vagina and inner labia make mucus etc. to lubricate and moisten these areas. Estrogens may induce additional mucus production. A combination of less bleeding & more mucus production might make the mucus more visible. As long as the mucus is clear & you don't have other symptoms, don't be alarmed.