Period blood while wearing pad stained underwear&after a day the blood in underwear turned green w/odor. I usually wait awhile to change pads. Problem?

Unclear. The cause of this is unclear. Schedule a visit with an Obgyn who can test your vaginal discharge for infection. Bacterial vaginosis and trichomoniasis can sometimes have a sort of greenish appearance. Yeast when thick can some times appear slightly yellow/green.