What kind of pain reliever can I give a kitten that is about 5 weeks or more?

I found a kitten and and it is thin. I can't get it to eat anything or get it to drink anything (can't get it to open its mouth). The kitten also has it stomach swollen and it whines some times. I want to help it but I don't know what to do. Should I give it some human medicine? What should I do?