A few words : Take him to the vet!

Honstly, He seems as if he needs it.
Money short or not, you're the one who brought him into your home, now it's your responsibility to give him what he needs.

It could look small and be something large -- It could be large and be something small -- You'll never know until he visits the vet and the vet knows how to treat whatever it is, big or small!

There's obviously something visibly wrong.