Dude, you said it yourself, you had the time of your life. So don't regret, just be happy and thankful to have such a great experience, not everybody is allowed to live such awesome moments. So enjoy your way back home, keep the good memories you built during this semester and love them like a treasure.
It's hard to leave the girl you love I understand. But maybe you can save some money to visit her in April or something, and then she comes to you this summer. Also try to apply for a job or studies in the same city as her next year. 6 months is not impossible to overcome if you're really in love