2 year difference

Sooo my boyfriend and I have been dating for 5 months now (known each other for 2 years... weird story lol) But anyways I am 2 years younger then him and I'm in grade 10 while he is in grade 12. And I know it's dumb but I am terrified for when him graduates... I mean who knows if we will still be together. But, I can't think about it without getting that weird feeling... Life will go on but any words of advice? Just afraid that he'll leave and we will never see or talk to each other..... thanks for reading!