Spots are not your fault. They happen entirely naturally because you're growing up. 9 out of every 10 teenagers get them at one time or another. Even some grown-ups get them. Even famous beautiful people get them, behind all that professional makeup.
Normally, the sebaceous glands that are in your skin make stuff called sebum to keep your skin slightly oily. Sebum protects your skin and hair from drying out. Your sebaceous glands live all over your body near your hair follicles (the roots your hair grows out of). When you're in your teens, your body makes extra hormones called 'androgens'. These tend to make your sebaceous glands go bonkers and produce far too much sebum. Your skin gets greasy and the hair follicles get blocked up. At this stage it's a whitehead or blackhead spot.
If bacteria get inside the blocked follicle, it all gets infected and you get those nasty red or yellow spots. It is also a hideous law of nature that you will always get a spot just before your big date when you want to look your best!