That might be excessive.
Tuna is known to contain small amounts of mercury. By eating 2 tins a day, you are very likely increasing the amount of mercury in your body (poison).
I would not eat more than one can if I were you. A good idea, if you have been doing this for a long time, would be to go and have your blood checked for mercury levels. Someone I know (a body builder) Used to slam tuna like it was nothing. He got very ill and doctors said it was due to mercury poisoning.
Why not use one tin and find some other protein sources as alternatives.
Getting it checked out might be worth the hour or so that it takes.
All the best.