Lump in breast

Sarah • ❤️💕
I was self-checking my boobs this morning (as I do usually every couple weeks) and I noticed a small lump on the underside of my right breast. It's about the size of a small olive, relatively soft, and I can move it around. I tried to see if it was also on the left one, but it's not. It feels like it's attached to the breast tissue, but still moves with my boob when I move it (if that makes any sense). It's hard to tell if it's just part of my breast tissue, or a separate mass. I am seeing my gynecologist on Monday, but I'm currently pretty worried. I'm only 19, healthy and active. I was wondering if anyone had any advice or encouragement.