Hi guys,

I've begun suffering of a sharp pain in the left side of my chest, I'm assuming it's my heart, it happens when I take deep breaths mainly or lay down on my stomach.

It started a few days ago, I'm not sure if it's a result of some sort of muscle restraintment due to heavy workouts or something else, I'm 21 and I work out every other day, What can this be?

If it worsens with a deep breath it is costochondritis, an inflammation of some tendons or ligaments in the chest. It hurts a lot, often for quite a while (weeks) but goes away on its own.
Take some naproxin (ALLEVE); it helps a lot with the pain.

In the future try stretching your chest well, arms overhead, before your workouts to avoid doing it again.

It is almost CERTAINLY not your heart. Heart pain never worsens a lot with a deep breath or a change in body position.

I have had this kind of pain when i have had pnemonia.