Skipped period on birthcontrol...been bleeding for almost 3 weeks now...?

okay so i skipped my period on birth control by just starting my new pack instead of taking the placebos....im in the 2nd week of my new pack and ive been bleeding since two sundays ago and im starting to get worried...ive skipped it before and had breakthrough bleeding but its only lasted a day or two...ive been on the same birth control for two years so i dont know why this is happening...any answers would be appreciated...thanks