I don't know if you can find a worse two year stretch in MSU's football history. Probably have to go back to the 1960s.
Based on quick Google search:
1987 and 1988, Rockey Felker
5-17 overall, 1-12 SEC
outscored 591-341
2002 and 2003, Jackie Sherrill
5-19 overall, 1-15 SEC
outscored 810-452
* in 2003, we lost by an average of 26.3
2005 and 2006, Sylvester Croom
6-17 overall, 2-14 SEC
outscored 568-374
I graduated from Mississippi State in 1990, so I remember each of these seasons fairly well. Just thinking about any one of those seasons is like a kick in the nuts.
However, the absolute worst two-year stretch belongs to:
1967 and 1968, Charles Shira
1-17-2 overall, 0-10-1 SEC
outscored 519-198
* in 1967, we scored 49 total points in 10 games (shutout 4 times)