Bam Margera -- I Think My Naked Stalker Gave Me Herpes

Bam Margera is convinced the naked chick who broke into his house and masturbated on his floor ... might have left a little gift behind as well -- HERPES.

Bam and his friend Tony Hawk posted a video on YouTube ... where Bam tells Tony everything that went down the night his alleged stalker was arrested two weeks ago -- including the part where she pleasured herself in front of him.

But then the "Jackass" star drops a bombshell -- he says he woke up the day after she busted in with a giant sore on his bottom lip.