Yes we all go through the idea we need to change something - less fatty foods, less booze, more exercise, etc . However stay off the internet and stop diagnosing yourself. It's only going to make you feel worse. If you are in need of a check up go schedule one asap. Try not to overthink and maybe check online for some fun new recipes that may interest you. Pinterest is great for that!

And FWIW I ate tuna literally daily for about a month and I never got mercury poisoning. Not saying it's ok to do, but I'm okay and am/was fine.