Uni Boyfriend

I've been with my boyfriend for a year and a half now, but he's gone to uni and I'm still in my last year of high school. I do know that I love him but he's only been gone 3 weeks and I'm really struggling. I even went up to see him last weekend and it was great but I still feel scared that we're going to break up soon, and then I get worried that I'm letting this affect my feelings towards him. 
Our sex life is great and I'm sure I do still love him but sometimes I get so confused between missing him and kinda being envious of him I don't know how I feel anymore. Anyone got any advice or just something that could help me out?