My car feels and hears like there is a brake line leak in my right rear brakes, but I don't see a puddle. Is it inside the drum or is there just air in the system? What am I looking for if it is inside the drum?

Remove the drum and look for a leak. If there's a leak, the shoes are probably soaked with brake fluid. You may want to peel back the wheel cylinder boots and look for leakage. Rebuild or replace the wheel cylinder, if needed. Afterwards, bleed the brakes, which should be done every two years. Be sure to also check the fluid level in the master cylinder reservoir.