I believe this is the the soldier you seek. He is enumerated in the 1860 Choctaw County Census as a 23 year old farmer.
There were two units known as the "33rd" in Mississippi and only this one was at Perryville, see the capsule history at the bottom of this post.
Drury J. Langston (First_Last)
Regiment Name 3 Batt'n Mississippi Inf.
Soldier's Rank_In 1 Lieutenant
Soldier's Rank_Out Captain
Film Number M232 roll 23
He may also be listed as a member of Company D according to another source.