8 days late for period, never late and also on birth control. on same kind for 3 yrs. i have bad cramps, white discharge, bad backache negative tests ?

Get a pregnancy: test now. If negative, wait a week, then check another pregnancy test. Just because you have been on birth control pills for 3 years does not mean there can be a failure. Your hormones are likely in flux though, which mean you will have to hang on until it re-establishes itself. If it continues, then talk to your GYN. You may also have infections that can throw off your cycle.