You need to learn some methods for guiding your own thoughts. You mind is like a garden, and your thoughts are plants. If they please you, water them and nurture them. If they're harmful, get rid of them. And make sure you pull them out by the root so they don't grow back.

Here's a method I taught myself that's sort of like a meditation. When you notice a distressing thought, take it out on its own and inspect it.

"I consider them tumors" lets just objectively look at that. Is it true? Are breasts tumors? No, of course not. They're a perfectly normal part of a woman's body. Is it helpful? Not really, it makes you feel negatively about yourself, about being seen, and it's leading you to consider drastic surgical intervention. What emotion is it based on? These things are growing and you don't want them there. You cant keep repeating something in your mind once you know it's totally not true, so rephrase it into something that is true: "I consider my breasts to be a perfectly natural growth that I'm uncomfortable with."

Let's do the second one, "They shouldn't be on my body" Is that true? They're breasts, you're a 16 year old girl. Is it true or is it false? Is it a helpful thought? Is it making you feel good or helping you to achieve something that you want to do? What emotion is it based on? Now rephrase that thought into something that's genuinely true. An example might be "even though breasts are normal body parts, I'd rather I didn't have them."

I was very interested in the macabre when i was younger, go with it. I second herbalism and taxidermy as great hobbies to focus your energy on.

Your body is for getting around in. You only look at it for a few seconds a day. Don't risk impacting the other 23 hours, 59 minutes and 45 seconds for vanity. No surgery is risk free.