How to handle stress being away from my ex girlfriend?

me and my ex was together for 2 years and a half.we broke up 3 months ago but we started talking and i seen her this saturday for the first time since we broke up.she spent two nights.we both cried this morning because we hate being away from each other.she lives in new jersey and i live in new york.she had 2 leave because she has school but she said she coming back friday.im taking it the hardest because i hate being away from her.it was the reason she moved in with me because we dont like being away from each other.I never felt this way about another girl before.I'm sittin here now stressed and missing her and crying.how do i handle this stress?