Jesse James' ex-wife Janine Lindemulder begged Jesse's sister to hook her up with painkillers in 2008 to "numb" the pain of the couple's nasty custody battle ... this according to emails obtained by TMZ.
In the emails, Janine pleads with Julie James England to ask her husband, Sgt. Mark T. England -- a medic in the Army -- to hook her up with Vicodin so she can "dissappear [sic] from all of this for a while."
Julie shoots Janine down, writing, "mark would never jeapordize [sic] his position by doing this! I love you and know you are having a rough time, however this is really weird you'd ask this of us. sunny needs you to be 100%."
As we first reported, Jesse filed legal docs on Friday ... trying to derail Janine's attempt to regain shared custody of their daughter Sunny. He paints Janine as a drugged-out mess who poses a serious risk to their daughter.
The next custody hearing is set for June 17.