'Panic! at the Disco' Drummer -- I Checked Into Rehab for 'Serious' Pill Addiction

One of the founding members of the rock band "Panic! at the Disco" says he just completed a stint in rehab after developing a serious addiction to prescription pills.

Drummer Spencer Smith just revealed the news in an emotional blog post ... saying he first got involved with drugs and alcohol when he was 19, just 6 years ago, but it quickly consumed his life.

The drummer says things really began to spiral out of control after a traumatic experience involving a loved one's health a few years later -- and he began to self medicate with a "dangerous amount" of Vicodin and Xanax.

The 25-year old says things got so bad, he stashed backup pills in every location imaginable ... and couldn't go more than 8 hours without going through withdrawals.

Smith says he checked himself into a treatment center last Fall -- cleaned himself up -- and is now focused on staying healthy and substance free.

Smith attributes his success to the support of his family and friends ... and plans to hit the road later this month again with the band in support of their new record.

The rocker adds, "My goal in releasing this is to try and relate to anyone who has experienced addiction personally or with a loved one, and to be honest with everyone else."