I know what you mean. I always worry about my cat who is at my mom's house because he's very old. He's 12 years old and I don't want to randomly hear the news that he died. I'm always paranoid that a pet is going to die and I won't be able to be there when he/she passes because a few years ago, I was in a mental facility and my dog died when I was there and I didn't get to say goodbye to her. She was the best dog ever. I talked with her when I didn't want to talk to anyone else, she was there when my parents split up and when my grandpa passed away and then when I lost her, I lost my best friend.

Is there a possibility you could take your cat to the vet and find out what is real instead of choosing to worry about what might be? Fear and anxiety can be immobilizing, but while you're choosing to worry, your precious companion isn't receiving the care she might need right now. Or the bumps could be not important at all. My point is that taking action trumps worrying every time.
Are there activities that you enjoy? Do you like to read? Perhaps you could join a book club, and choose to speak to one person at a meeting, then work your way to more often if you're nervous.
Take it from someone who knows, loneliness is one of those problems in life we can do something about. It's hard - I get it, but it's in our control to change it, one conversation at a time :)