Possible colon cancer?

I'm 16 male with really no family history with cancer. I recently noticed thee small bumps below anal opening. They don't bleed or itch. I was really scared that it might be cancer. My mom got desitin and it seems like one is going down. I have also had lumps under my arms. I have been to the doctor at least three times in the past six months. The last time the doctor seemed annoyed and got a blood test done and she said it came back clear. I told her that I was afraid I had cancer but she insisted otherwise. So now like two weeks ago I noticed these three lumps. Maybe the size of a pea. They don't hurt. Last week I noticed a small streak of blood on the stool and today there was a small streak but the stool looks fine. But when I noticed the blood the first time it was a hard stool and today again it was a hard stool. I'm so scared I might have colon cancer or anything and I really don't want to have cancer. Please I'm desperate for help. I don't really want to see my doctor again because I'm afraid she might not take me seriously. And i dont want any surgery done.