Hey I study health & exercise science at uni.

Firstly, if you actually are doing your weight programme correctly, 7days a week is absolutely not advised, ecspecially due to your age.

Muscles, after a work out incur little tears, the muscles continue to grow for 48 hours. So really, 3 to 4 days a week is right.

Theres different ways to gain bulk, endurance, and strength to muscle. Your concerned with bulk. So you should be doing 8-12 reps (after about 12 reps you should really be struggling, so make sure your wights weigh enough) with 3 sets. (strength would be 1-4 reps, endurance 12-1.

If you want to look bigger fast, focus on your upper body, shoulder area.

Any other specific questions id be happy to help

15 years old?? I wish I had started lifting weights at 15
i am 28 and trained for fitness competitions for 3 years, lately I just enjoy lifting weights, eating right and being active.
I am 5'6 and 115, which I am ok with. (because, honestly...There isn't a 140lb class for ladies in my level of competition...Wouldn't mind getting back the 5lbs. Of muscle i've lost though.Lol oh well)
it sounds like you have some of the right ideas. As matt182 mentioned, your body does need to rest. I know it sounds impossible to make any gains with working your muscles once a week--but they do need time to re-grow.
Set up a program for yourself. This is mine: 1) back and bicep 2) chest, triceps, delts. 3)legs. Abs are done twice a week. And when I was training I broke the once-a-week rule. One group would be done twice a week with atleast 2 days in between. Ie)1 week: 1,2,3,1 2nd week: 2,3,1,2 etc.. With rest days and cardio inbetween.
This is what worked for me.
As for the supplements I took creatine, and protein supplements. I couldn't tell you where I got all my info (specifically) but I read about splitting the creatine. I would take half before my work-out and the other half right after. I also ate atleast 15g of protein within an hour of my work-out.
As a girl it is alot harder for me to put on muscle mass. I would eat alot of salmon, tuna, egg whites, cottage cheese, and my protein bars and drinks.But I made sure I ate good carbs too, this is where you get your energy from. ***don't leave out a food group, it's just like lifting weights, don't leave out a body part. Sorry matt182, I have to disagree on that one, I see soooo many guys with great upper bodies and chicken legs, it looks ridiculous!!
the program that I followed was strict, but I enjoyed it at the time, so just have fun with it, make sure you eat enough and get your "rest" days in. Good luck!!!

Haha yes true, although I didnt mean to imply not doing your lower body :d