Is mackarel canned fish healthy? i eat 2 cans a day ? been eating like that for 5 months? will it damage my kidneys or i shouldn't worry about it?

Mackarel: is an oily fish high in omega-3 fatty acids and typically less expensive than salmon. I don't really know how large your cans are, but I would think you are consuming more than 600-800 cal/day, or perhaps 1/4 to 1/3 of your daily caloric input. This is too much of any one kind of food(even a good one) for a balanced diet. And it's a lot of fat (even the good kind) and protein. I would cut back.

Mackerel: Mackerel itself is fine to eat but in the US there's been a warning of king mackerel containing mercury which makes it unsafe if consumed in larger than recommended amounts. If you don't live in the US, this warning may not be valid for you, though. Atlantic mackerel seems to be OK. Here's a good link http://seafood.edf.org/mackerel for you to read & educate yourself.