If your wanting to build muscle, you need to LIFT weight man. The cardio's good but at your age it's less important than being on the weights. Pay attention to how many reps you're doing in each set. Basicly you have two types of muscle fiber in your body. Fast twitch muscles, and slow twitch muscles. It's the fast twitch muscles which provide size and bulk to your frame. Building muscle is a process of tearing muscle fiber through weight lifting, and then allowing that fiber to recover or heal during a recovery period. High rep, low weight exercise targets your slow twitch muscles, these are your endurance muscles. If you want to get big, you have to target your fast twitch muscles. To do that you need a high weight low rep program. If your doing more than 5-7 reps in a set you don't have enough weight on the bar. You need to stack the weights until it's almost impossible to get them up. It's needs to be a struggle or you're not working your fast twitch muscles. Also just because they're called "fast twitch" muscles doesn't mean you have to lift fast, lift in a steady safe manner. Try to get a workout partner to spot you, or use a self spotting machine for the more dangerous exercises, i.e. bench press and squat.
Now you have the recovery period. You should never work the same muscle group two days in a row. You HAVE to allow the muscle to recover. Remember you're tearing the muscle fibers. If you tear them some more before they heal, you've haven't done any good. And you have to feed your body the right foods to fuel that recovery. The diet you described is SHIT, man. You should stay of the pizza for sure. You need PROTIEN, PROTIEN, PROTIEN! The former poster mentioned whey protien, that the bomb for building muscle, other types are good for mantaining it. You'll find whey protien at your local supplement store. It comes in powdered form that you mix with water or milk to form a shake. I recommend the strawberry, and mixing it with water. I once had it with milk right as I walked into the gym and went straight to cardio, I barely finished lifting before I almost puked. Anyway, the strawberry is great to blend with a bannana, which is another food you should eat a lot of. The multivitamins are a great start for supplements. I would also recommend Creatine. You can also find that at your local supplement store. Creatine is almost like a legal steriod. Be warned though, creatine will give you righteous gas man, so you may not want to take it on any day you have a date. It comes in powdered or pill form and is relatively inexpensive, as is the whey protien. If you get really serious down the road you might consider NO2, which is nitric oxide, also sold at any supplement store. Beware it is EXPENSIVE. Within one week of starting on it though, I added 50 pounds to my bench press. It works. It actually relaxes and expands your blood vessels, which allows more blood to rush to your muscles to speed recovery time.
I found most of this information a couple of years ago on the Men's Health website. Check it out, they have some great tips, exercise schedules, and diet ideas.
Good luck to you.