At ur age & gender (21F), the chances r overwhelming in ur favor that this is not cardiac chest pain (esp with a neg test).
I would focus on a careful breast exam by a gynecologist & then TTYD about other possibilities like acid reflux or lung disease/bronchitis (esp if u r a smoker). Lastly, muscle strain is possible depending on activity level & which exercises u perform. GL & thanks 4 ur questi
Would you like to video or text chat with me?