Relationship anxiety!!!

I'm currently 8 months into a relationship with the greatest guy I've ever met! I love his family, his interests, his zest for life and we get along super well - basically the same person just boy vs. girl! 
I have this weird anxiety about our relationship and I don't know what to do :( I keep having weird doubts about him even though I'm crazy about him! Bare in mind, this is my first relationship and I have no idea how I'm supposed to be feeling!!! He's my favourite person ever and I love being with him/get excited about seeing him even 8 months into our relationship.
Everytime he has to leave I freak out and panic about what I'm supposed to do next! I get super anxious when he's not around! And then super doubtful. It's ridiculous! 
I've been on and off antidepressants for the last six months and nothing makes me excited anymore. My boyfriend is effectively my life! I somewhat hate it. But I love sharing things with him.
I guess I'm just looking for clarity on doubts in a relationship! I know everything isn't always roses, but I really don't want to give him up!!! :(