First period after hysteroscopic myomectomy, 2nd day extremely heavy. cramps for 8+hours! what gives?! on tranexamic acid now, why is this happening?

Post Myomectomy AUB: If you think about the surgery you underwent, a fibroid (with overlying endometrium) was removed from the muscle of the uterus leaving a defect. That whole area has to heal and regenerate in such a way that it will again function normally. That may take a couple months so this menses may not be representative of how the rest will be. Generally it takes 6-8 weeks to fully heal.