Can you help me please to get distressed?

Umm,where do I start? I am in a relationship for a year now.. I should say that I am only 16,but please dont underestimate this 'cos of my age. I am worried because I feel like I am too much in love if you could say that. I love my boyfriend very much. I find a great friend in him,and only person that knows me best,and understands me best. He is always there for me and we have so much fun together. I could say that everything is just perfect now. But there is a thing that bothers me a lot. I think about losing him too much. Now how could i bring it closer to you. Sometimes I feel so so so sad because I think about the future and I am aware that I have ONLY 16 years and that I will lose him any time. And I dont want that to happen,because he is everything to me.. Maybe you wont understand because you think I am too young,but no. I LOVE him,really. It isn't just another story how spoiled kid is talking too much about love and she doesnt even know. IT IS NOT LIKE THAT. Its like I've already found my soul mate (if that even exists) and i just dont want to lose him. and i think too much about that :( Too much. Even now when absolutely everything is perfect. I just cant stop myself from crying at nights because i fell sad :/ I dont know whats wrong with me i just fell like he is giving me everything I need. I already said,love,friendship,support, happiness,joy,fun,security,I fell safe around him ! All this is fine and i cant stop being sad about a brake up that will necessarily happen in future.. I mean there is no reason but i just fell sad :/ And it gets worse when we have a little argument,at that time i see what could i lose and i dont like it I HATE IT :( How can I get destressed and just how can I enjoy in all this without stress :( HELP PLEASE and thanks a lot for your time :) <3