TMZ has obtained a copy of the police report taken after Johnny's body was found in his New Mexico home this weekend -- and according to the document, Teresa's suspicions stem from Johnny's longstanding drug problems. Teresa said she had no evidence to back it up.

Police found no proof of illegal drugs in the home, but did come across a locked safe filled with prescription meds -- including Hydrocodone (generic Vicodin) and Quetiapine (a drug used to treat schizophrenia).

Cops say they also found a Hydrocodone pill by Johnny's body.

Family members told police Johnny had been complaining of stomach problems in the hours before his death -- which might explain the Pepto Bismol cops also found on the scene.