Chest pain? im only 21 years old?

so I started feeling chest pain, discomfort on my chest and I layed down and rested .I got really scaredm because its something I have never experienced and I counted my pulse and it was 36 beats per minute though I am a very athletic person, and then in addition I felled asleep and when I woke up I woke up with a very loud heart beat not fast just a big loud one.. and my breathing was also short. Does anyone know what happenned?