I'm only 15, and am a believing Christian... my problem is that I'd like to wear a crucifix around my neck, and I know that most Christians do, anyway, but is this considered idol-worship..?
The first question that comes to my mind is, "Why do you want to wear a crucifix in the first place?" Is it because "most Christians do"? Actually, that would not be the case. Many of your friends and acquaintances may wear one, but are you only trying to conform to what others do? This may be addressed in Romans 12:2, although you may object that you are not conforming to the world, but only to the practice of other Christians. Nevertheless, I would not let peer pressure be a factor in my decision.
The other problem I would have is a problem that many Christians have with a crucifix in the first place. Many Christians wear a cross. The cross is empty. That is because our Lord died on the cross, was buried, and then rose from the dead. Why portray a Christ who is still on the cross. He said, "It is finished." A crucifix suggests that it is not. Our risen Lord is portrayed in an entirely different light in Revelation 1:13-18. He is "the living One, who was dead, and behold, is alive forevermore (1:18). We see Him again in Revelation 4 & 5, a glorified Lord, not one who is on a cross. When Jesus appeared to His disciples, He did show Thomas the marks in His hands, and the scar in his side, but He was alive and glorified, not dead.
It would be like carrying a picture of Jesus in the tomb, rather than a picture of an empty tomb. He is risen!
Now, I have not forgotten your question. Essentially, you are concerned that the crucifix may be an image of our Lord, and images are forbidden in the Old Testament. I fear that for many, a crucifix has too much value in and of itself, and that this does detract from a focus on our glorious, risen Lord. I might be willing to call this my personal conviction, but this is surely an issue you should consider.
J.I. Packer has a chapter in his excellent book, Knowing God. I've loaned my copy out, so I don't have it with me. Nevertheless, I think he has an excellent chapter on the invisibility of God. I would strongly suggest that you take a look at this chapter as you consider what the Scriptures teach.
I have a chapter on the invisibility of God, but I have not directly addressed the matter of images, as has Dr. Packer.
See also Romans 14.