I would highly recommend you stop eating 5 cans of tuna a day. Thats just asking for mercury poisoning right there. IMO I'd cut that down to 1 can of tuna/day at the most. Replace those other 4 cans with lean ground beef, lean steaks, chicken, turkey, or other fish (salmon, tilapia, flounder, trout).
First thing first boss, red meat contains a lot of minerals and omegas that your body requires. Obviously you don't want to consume large quantities of fatty red meat, but a steak here and there and lean (93% or better) ground beef is an excellent option. And the fact that you're trying to gain weight you could even dip to 85-90% lean ground beef. Another alternate is lean ground turkey which you can find at nearly any grocery store.
Chicken man. Lots of chicken. Easy to cook, low in fat, and high in quality protein. Just stick a bunch in the oven and bake them, then toss them in tupperware to eat throughout the week. Choose your own seasoning or even dipping sauces since you're on a bulk.
Fish should be a required part of everybody's diet, but many people do without. Salmon is a fish high in good fats. And something that is not well known outside the bodybuilding industry is that you NEED good fats to build muscle.
Eggs are also a great source of solid protein as well as healthy fats, but you are already eating them so no need to go into detail there.
With each of these meats, add a complex carb source. You're bulking, so eat wheat pasta, potatoes, sweet potatoes, oatmeal, Quinoa, rice, or Ezekiel bread.
In addition to your meat, your complex carb source, add veggies. Nothing stokes your metabolism and has so few calories as green veggies like broccoli, grean beans, and leafy greens.
Lastly, add some additional good fats. Fish Oil, Coconut Oil, Grapeseed Oil. If you'd rather just eat things as opposed to dosing oils, almonds, natural peanut butter, and the fish mentioned above. If you don't like almonds, try another form of nut (walnuts aren't half bad either).
If your plate looks like there is too much food on it, then you're making a start. Too many people underestimate what they are taking in. And for some people (I was 5'11, 150 up until my third year in college) its necessary to eat very far over maintenance calories to gain weight.
Here is an easy way to start. Build three solid meals. You said you are already eating eggs and wheat toast for breakfast, a good start. Add more egg whites, as you don't want to eat too many whole eggs everyday. Add some form of fruit. And slather natural peanuts butter on your toast. At lunch have a large serving of fish/chicken/beef with some complex carbs and veggies. Then repeat for dinner.
Then build three simple and quick meals. This is where a can of tuna, and some fruit. Or a home-made weightgainer shake will come in handy.
I find its easier to start if you only have to build 3 large well balanced meals. Obviously it would be better if you built 6 large well balanced meals, but thats not always possible. So start with the three meals and add those shakes. There are plenty of good shake recipes on the board and everyone here has one they swear by. A simple but easy one is to grind up 1.5 cup of oats in a coffee grinder, add in milk, peanut butter, and some whey protein. Its a simple and easy ~500 calories. Three of those a day is 1500 calories added to three well balance meals should have you sitting at about 3500 calories.
Good luck boss and feel free to ask anymore questions you may have as there are plenty of guys and gals on here with a ton of experience.
