I'm not quite sure what people mean when they say "eat more"

I might tune up the lunch a bit (you can do better than 3 slices of pepperoni pizza), but it looks ok. I would assume you're young (25 or under)? Give it time. Maybe eat a nutritious snack before bed. Throw in some more vegetables. Generally speaking, weight will come. If you're naturally slim, consider it a blessing. I was in the same boat. I wanted to gain mass and had the hardest time until I aged and my metabolism slowed.
From my experience: guys who were big and bulky when young, end up being fat when they age a bit. The voluptuous high school cheerleader almost always is overweight 10 years later. People who are slim/skinny when young often age into a nice body.
It's also very hard to gain weight while losing body fat. Usually it's one or the other.

Hit the heavy compound exercises when lifting. Squats, deadlift, cleans, dips, pull-ups. Go heavy, then go home and rest.

It kind of sounds like you know what the problems are already

Your diet sucks. Too many energy calories (fat/carbs).

Unless you just started working out, trying to add any significant muscle mass while dropping fat is a losing proposition. Choose one or the other or you'll most likely fail at both. Clean up your diet also. Your breakfast is full of fat; switch out the bacon for lean turkey bacon and eat some kind of low fat greek yogurt (Fage or Trader Joe's are my preferred brands) instead. Same with your lunch. I'm not certain why if you're trying to lose fat you're still eating pizza. Granola bars are crap too.

You are old enough to drink and your dinner consists of what your mom makes? So you live at home?

dude, you answered your own question:

to gain weight, you have to eat more calories

to lose weight, you have have to eat less calories.

how do you expect to gain muscle (gaining weight) while losing fat (losing weight?)

your diet is eh, but given that you live at home, it's probably not going to improve much.

build, then cut, build, then cut....

I'm a bartender and in college, yet I still manage to eat healthy and not drink more than 1 alcoholic beverage per night. What's your excuse?

Is there some unwritten rule that you have to get trashed on the weekends to enjoy yourself while going out? If anybody gives you a hard time about being 'lightweight' give them a hard time about something they do.

Generally speaking once you get past that beginner phase where your body is willing to lose fat and put on muscle at the same time, its very very hard to do that. Your diet needs to be really on point and your lifting needs to be intense and frequent and you need to sleep a ton. Really the only way I've found that I can do this is following a paleolithic diet, with roughly 40% cals from protein, 40% from fat, 20% from carbs with no bread or anything containing flour, low glycemic fruits and lots of veggies. That probably doesn't sound like something you'll be willing to stick to.

So just accept the fact that muscle gain is going to be accompanied by fat gain. Break down what are called your "macros" (the ratio of calories from protein, fats, and carbs to total calories consumed) and shoot for 30% fats, 30% protein, 40% carbs. Clean those carbs up too, no need to be eating pizza and sugary yogurt or potatoes. Basically use nutritiondata.com to find foods with low glycemic indexes and try to stick to those as your sources for carbs.

Make sure at least half of the number of total sets you are doing are heavy compound lifts. You can throw in some bodybuilding isolation exercises to get a sick pump or whatever, but at the end of the day its going to be those 4 sets of 6 deadlifts that shock your body into producing more testosterone and adding muscle all over.

Good luck.

Dude, if you're not pledging a frat that particular semester, there's no way you HAVE to drink 8 drinks a night on weekends. Do the old "hang on to the same beer the entire night" trick.

what an irritating misconception. first of all, noone makes you drink, if you dont want to, dont...noone cares. Second, Fraternity men appreciate pledges who are sober to lend a hand with driving...Safety first.

Driving is a good excuse btw, esp. if you drove your buddies. But yeah, diet isn't great.