How can i stop being a worrier about my dog?

Well, in my opinion you should just think about how much you love him now. If you lurk in the past then you can't live your life and love him now. I completely understand, a similar thing happened to me. If something serious is happening then you'd know about it, so don't worry. Just love him and care for him, and he'll be happy. When it is time for him to go then he will, and he'll be happy, and you'll see him again, so just don't worry. I know this is hard but you just have to be in the moment and love him. I hope this helps, good luck!