how to cope with missing your boyfriend

so my boyfriend is going out of the country for three weeks and i’m really sad about it and i’m going to miss him. He’s basically my bestfriend and my boyfriend and we hangout and talk all the time and i don’t have many other friends where i live. it’s going to be really hard coping with the fact that i’m not going to get to talk to him a lot and might not even talk to him some days because he’s not going to have service. People keep telling me “distract yourself and go hang out with your friends!” but they don’t realize that i don’t have many real friends. i don’t do well with missing people and i need advice because i don’t know how i can handle missing him for 21 days.