hello everyone, i found the answer!!!
Just in case if anyone gets stuck with the same query
i converted the smalldatetime column in the same way the variable was converted!
cast(CONVERT(CHAR,DATEADD(d, -1,DATEADD(mm, DATEDIFF(m, 0, SMALLDATETIMECOLUMNNAME + 1,0)),112)-19000000 as int) = @LowDate
It worked!
any suggestions on this are welcome:-)