If you cannot afford a vet, please surrender your puppy to a local shelter so he can get the proper attention, and please do it quickly. He sounds like hes in a lot of pain, and doesn't deserve to suffer. Please do the right thing for him.
True, if you can't afford to care for a pet you should wait until you can. That being said, you now have a sick puppy that needs medical attention and I am sure you don't want to see it suffer. Try contacting a Vet to see if they will take payments or can recommend some place in your area to take it. Mif not, do go to your Shelter or call the SPCA.
You could always try your local animal shelter. Sometimes they have list of discounted vets that you could take your puppy to. Your puppy needs to go to a vet of some sort or I'm afraid you may loose him.
If you only have a small income where you cannot handle vet emergencies, you probably should not be having a puppy in the first place. That's the reality! Giving him ANYTHING at this point could be extremely dangerous; get him to a vet!
Get your puppy into the vet!