Anxiety over (soon-to-be) long distance relationship

Hi all. So I'm currently finishing up a semester study abroad in South America, heading back to the US in two weeks. I met my now-boyfriend here about 2.5 months ago. He's from another Spanish-speaking country, not the one we're in now (think: American girl and Peruvian guy meet in Colombia) and will be heading back to his own country just a few days after I leave for mine. We're going to do long distance, with the plan being for me to visit him in August and him to come visit me in December. The relationship itself is good: we have a lot of things in common, are really into each other, have a great time together, and have established very healthy communication.

Despite that, however, I'm experiencing an incredible amount of anxiety over this relationship, and have been since the beginning. I can't even count all the roots of this anxiety: fear that he doesn't like me as much as I like him, fear that he's lying when he says he loves me, fear that I'm not good enough for him, fear that I can't help or support him, fear that he's going to break up with me for one of a gazillion reasons (that I'm too emotional, that I'm too affectionate, that I'm not affectionate enough, that he's going to fall in love with somebody else once back in his own country), fear that I'm going to do something to mess up the relationship, fear that he's going to decide I'm too young for him (there's a 6 year age difference), fear that one day he's just going to decide he "can't take" the distance and dump me. Etc. Etc. Etc. I've been honest with him about this anxiety, and he's been nothing but kind, loving, and reassuring. Every time he reassures me, I feel a huge wash of relief for about a day, and then the fears start to creep back in until I start to feel sick again. While I don't regret being honest about these insecurities, I don't want to be constantly burdening him with them either. I don't want to fulfill that stupid, false "high-maintenance girlfriend" stereotype. I just want to enjoy the feeling of being in a relationship with someone I love and not be constantly crying/sick with worry that I'm going to lose him.

Anyone else have similar problems, in a long- or short-distance relationship? How have you worked through them? Also, any success stories (again, long- or short-distance) would be appreciated :) :)