Can you tell me is eating sushi too often bad?

Depends: Depends on who you ask. The japanese culture would likely say no, however western medical doctors may speak to the consequences of higher mercury ingestion as a result of increased fish intake.

Low-Mercury fish.: The main concern with sushi is obviously the chance of bacterial infection in the context of eating raw fish. Those who make sushi for us to eat undergo rigorous and lengthy training in order to prepare the raw fish in a way that minimizes the chance of infection while allowing us to eat such an awesome delicacy, if you eat it often, focus on low-Mercury fish.