There are a couple ways to do this. What works best depends on your data. You can use sortrows to sort your table keeping rows together.
Option 1 - add a year column, Sort by year then month. Use sortrows,
Option 2 - turn your month variable into a categorical, and define a category order using either the 'Ordinal',true name value pair or reordercats function. You can then sort using sortrows,
