I have a question about a septic tank?

I have never lived in a house with a septic tank. I was told normal use of the bathroom would not cause any issues with the tank. I haven't put anything unusual in any of the drains. But for some reason my house around the bathroom smells like sewage. Its more fierce coming from the air vent. Am I having a septic tank issue? If so is it backing up? What should I do?