Jenna Jameson -- I Wasn't High on Pills ... I Was Just Tired

Jenna Jameson is adamant she was NOT whacked out on prescription drugs during her bizarre live TV interview yesterday ... telling TMZ she was just really, really tired.

Jenna was like a completely different (and lucid) person today as she continued on her book tour -- unlike her slurring, bumbling, confusing appearance on "Good Day NY" Monday morning.

When asked why she seemed so sloppy on the show, Jenna simply chalked it up to exhaustion.

In fact, during an interview yesterday Jenna said she hasn't done any drugs in 7 years.