Dude, you're so thin that you NEED some fat. You're skin and bones.
You can study up on nutrition (frankly there's a lot of quacks and anything worth doing should be worth doing well) by googling on nutrition and how it works. There's SO MUCH information about this stuff online that it's a real easy to study up on.
Insulin shuttles nutrition (amino acids and carbon chains...basically) in and out of the cell. When you eat, your blood sugar level when eating, and what you eat, determine whether nutrition gets utilized, or shuttled into storage.
E.g. a fat person may eat fewer calories than they need, and feel hungry, but, they eat the wrong thing. They starve all day, let's say (which is typical), and then they binge on something like chocolate cake. The icing on the cake is nothing more than Crisco grease, food coloring and large amounts of sugar...THAT...causes an insulin response which says....take whatever I just ate and STORE IT. So, the fat person isn't getting nourished, but, instead, they are storing even more fat. Fat does NOT burn calories, period, as muscle does, even at rest, so fat folks walk around with the coat of lard because they eat the wrong things at the wrong time.
In your case, you're very thin, and unless you drive your insulin up with fast gyclemic index foods, you sure aren't going to get fat. You're not getting enough to eat. STOP with that line of thinking. You EAT; EAT UNTIL IT HURTS; EAT EXTRA.
Want to stay lean? Lift weights! Resistance training is the ONLY exercise that increase your BMR, lean muscle mass, and strengthens your bones, AS YOU GROW OLDER. Want to stay lean? EAT! The saying goes, "fuel the furnace."
When you starve, you train your body how to become a fat-storing machine. That's why fat folks fail in diet. They don't understand metabolic activation.
In your case, EAT, eat, eat. Do resistance training. Bread is NOT going to make you fat when you're undernourished, and under-eating. Only if you douse it in sugar, and invoke an insulin response will it make you fat...otherwise, it's going to help you get healthier.
In addition to your bread, post workout, throw some grits, oatmeal, farina, brown rice, or some other slow carb / low glycemic index food in there along with some water. You do that a minimum of five times a day, and you'll see some progress. Post workout, a faster carb like white rice, and any fruit juice, are just what your body needs to be replenished in the "golden hour."
Quit worrying about getting fat.
I usually don't pull bread out of my diet until about 20 weeks out from the show.
YOU need calories. You're skin and bones.
Bring your carbs UP. Eat about 50 grams of carbs, at each setting, or even more, a minimum of five times a day. Instead of one piece of bread, you eat two.
Carbs are protein sparing. Glucose is your body's preferred fuel. Give it the glucose it needs to be healthy and strong.
Eat about 40 to 50 grams of protein at each meal, a minimum of four times a day.
Eat good fat: peanut butter, almond butter, nuts, avocados, oily fish. This will help you stay healthy.