Feeling empty

Hey guys, so im 16 years old and about 2 months ago someone i was in a relationship/situationship with broke up with me.  It was right around our graduation so it didn't really hit me at first, but a few weeks into vacation i started feeling it (or rather there lack of).  I feel like I've just been going through the motions, and i get this hollow feeling inside, like I've been scooped out.  When I'm with friends and family everything feels normal, but as soon as I'm on my own a switch flips and I'm back to feeling nothing at all.  It gets worse at night, sometimes I feel anxious and find it hard to breathe.  My hobbies (like going to the gym, playing drums, songwriting), friends and family help me keep on track, but I'm just not sure how to help myself here.