Right turn signal and right tail light both dont work

I was recently pulled over when I was told my passenger side tail light was out. I got a new bulb for it, my stepdad changed it and it still did not work. About August My stepdad and I installed a new car stereo I had gotten for my birthday. He seems to think its the wiring because the brake lights and turn signals in the back on the right side work just not the parking light/tail light. Also my front right turn signal doesnt work but the headlight does.