Am i obsessive or is it separation anxiety?

Me(14f) and my boyfriend (15m) have been in a relationship for almost three years now. Ever since we hit about 5-6 months i get overly anxious when my bf leaves the house or hangs out with friends even if hes just going to the store with his older sister. I know this isnt something i should be getting upset over and it is so hard to control. I fully trust him and i know he will not cheat on me but its just the thought that hes not home and idk whats hes doing like when he's at a sleepover i get upset because i constantly want to know what him and his friends are doing. I usually try to distract myself but its so hard to, does anyone have experience with this or have any advice