"Big Brother" winner Adam Jasinski just pled guilty in Massachusetts federal court for possession of oxy pills with intent to distribute -- and get this, the feds are also nailing the guy for dodging taxes in the process.
As we previously reported, the DEA arrested Jasinski last year for trying to deal 2,000 pills of oxycodone to a government informant -- and after his hearing today, dude faces 20 years in prison plus a $1,000,000 fine.
But that's not it ... the ex-reality star also fessed up to not paying taxes on his $500,000 in "BB" winnings -- which he allegedly used to back his drug business -- and could face another year in prison as a result.
Sentencing is scheduled for January 11 next year. Big Brother will be watching.