VIDEO : Jack Antonoff ?Seeing Someone Else? After Splitting With Lena Dunham

Jack Antonoff is reportedly already seeing someone else after his recent split from girlfriend of five years, Lena Dunham. An insider told Us Weekly, that ?the relationship is done and he has moved on, as in he is seeing someone else." While Antonoff has someone new in his life, Dunham is ?focusing on herself and her work," according to the source. The Girls creator and the singer called it quits on Monday, after half a decade together.