Please please please help

So first off, please no hate on this. I'm doing all that I can. Vets are closed on sundays where I live (stupid, right?) and I've looked everything up and can barely find any information so I'm turning to you all.

My dog has a ton of little bumps all over his back and sides. They aren't visible. He's lethargic. He's son wanting to eat.

Its not like him at all because normally he is a very hyper dog. His side randomly shakes too.

His nose is wet and he's still shaking his tail whenever I pet him. So those are two good signs.

I also gave him Benadryl, I looked it up and did research before giving it to him so I knew it was okay.

Is there anything that I can do? 😔😔 I feel so bad and I just want him to return to his normal self. I'm honestly really scared because he's my best friend.