You have a few options.
Option 1: Don't allow follow to turn off. Such as move into melee range, move behind, face mob in combat etc, all turn off follow.
Option 2: While you are in combat and need to move, hit the "F-Follow" (Force Follow) to turn it back on.
Option 3: Use OFollow (OgreFollow). It works much the same way as in-game follow, except face mob doesn't turn it off