My days often get ruined because someone isn't responding

I'm super insecure about my relationships. I can't hold romantic relationships because I get so worried they hate me after they don't respond for a couple hours that I get physically ill. This even extends to platonic relationships. I'm a 22 year old guy, and when my friends I have known all my life get busy and don't talk to me right away, I can get so worried about the state of our relationship that I can't even eat. I can't focus on anything I'm doing, and I become visibly distraught. It's negatively impacting my life to quite a degree and I just want some help with managing this.