I just got the new expansion and It won;t let me start because it says I have to leave my followers behind. But I don't have any one of them just dissapeared one day no idea what to do. Don't really want to start all over

Oh this will cause a bit of a problem.Do you have Dead money Dlc?My sugestiom is play it.Because your folowers automatcly leave.Or you can try use console comands to summon this missing companion and then tell him to leave.