Questions or concerns about your eating habits and health risks of certain foods can always be discussed with your primary care physician
. He or she can take a more detailed history of your current eating habits and help advise you about certain risks.
When it comes to sushi, you are correct that eating raw fish does introduce certain health risks. In particular, certain kinds of fish often used in sushi (such as tuna) can expose you to certain heavy metals such as mercury in higher levels than is considered safe. Pregnant women are advised not to eat tuna for precisely this reason.
Although government agencies have established upper safe limits for ingestion of mercury-containing fish, there is no routine testing that will let you know exactly how much mercury you are taking in with the sushi you eat. However, it is concerning that several studies done on restaurants in the New York area have shown that tuna sushi often has far higher quantities of mercury than is considered safe.
You should discuss your concerns with your primary care physician, but given the known risks of ingesting too much mercury, moderation is also a good precaution. If you are eating sushi multiple times every week that may be too much.