Complicated and defensive

Ok so I've been with my bf for almost 4 months now and I honestly have loved him since the start. But our relationships a little complicated, this is why; he lives in a different country to me and at the beginning of our relationship he said he would move to where I am in two years once he's finished college. As well as that I have depression and I think it constantly affects him and gets him down. The other day I Spoke to one of his friends , on FaceTime and I really hit it off with him cause he has similar interests to me. After that my be got this crazy idea into his head that I want to leave him for his friend. This then reminded him that when I go to uni I'm gonna meet a lot of new people and he thinks I'll leave him for them cause I'll "realise he's not that good". This is insane cause I love him to pieces and I can't imagine my life without him. Anyway when he feels like I'm gonna leave him, he gets really defensive and try's to leave me first, in an attempt to make himself feel less vulnerable. The thing is this really hurts me and I can't convince him that I'm not gonna leave him, I don't no what to do, please help.