Too attached

My heart seriously hurts. Me and my SO have been dating for 2 years. We were each other's only friends when we started dating so we are VERY close. We met at work. We work together every day. He recently got offered a better job and I am so happy for him but so heartbroken. I have anxiety and depression and he is my rock. He is always there. I just don't know what I'm gonna do without him. I'm not being selfish though bc I'm happy for him and he deserves the world so if he's getting something better than I want him to take it. But since this has happened my anxiety and depression has come back. I'm just so upset. I'm going to miss him. Being with him all day everyday. Most couples can't do it but we can. There isn't a day since we started dating that we haven't hung out. We are very attached and close. But I'm more emotional than him obviously. I know we're not breaking up but I'm just so upset. I won't be able to turn around at work and joke with him and mess with him. He's my best friend. I know I probably sound crazy but I just need to vent. I don't have anyone else to talk to. And if you don't have anything nice to say don't comment please. I don't need your negativity.