Is this Muscles Spasm or a Heart Attack?

Last night, I experienced a terrible sharp pain on my left upper back and chest area.
I was unable to breathe properly and continuously gasping for air.
Nose were blocked suddenly and I had to put on medicated oil to breathe again.
Initially, I was lying flat on my chest on the floor to play 'Candy Crush' then, I headed back to bed.
It started as soon as I sat on my bed.
The pain on my back is unbearable & I tried ways to move my body to a position where it could temporarily 'cease' the pain, but it became worst.
Lastly, I tried lying flat on my back.
The pain was minimized but I was breathing hard through my mouth.
Breathing through my mouth triggered the pain on my back. I called for my brother to get the medicated oil for me and reminded him not to tell my parents about it.
I just laid down there for quite long, gasping for air and not move an inch.
After what seems like an hour, I felt ok, so I tried to sit up and breathe properly.
Wrong, totally wrong.
The moment I used my arms to hold me up, the pain came back again.
I had no choice but to ly back on my bed.
Thousands of thoughts came rushing through my head.
"Am I having a heart attack?", "Why is it so painful?", "I've only experienced breathing difficulty last time round, but how come this time, it's the whole back?", What's wrong with me?"
All of those are negative thoughts.
Still, I slowly closed my eyes and tried to be relax and breathe.
& I fell asleep unknowingly.

This morning, the pain was gone.
No pain at all, nose wasn't blocked too.
Everything was fine now.
It felt like I had a war last night, with myself, with my body.
I looked up on Google to find out about my problem and I found this: Muscle Spasm.
"It most commonly refers to a muscle cramp which is often accompanied by a sudden burst of pain, but is usually harmless and ceases after a few minutes."
Cause of Muscle Spasm:
"Hypertonic muscle spasms is the state of chronic, excessive muscle tone, or tension in a resting muscle – the amount of contraction that remains when a muscle is not actively working."
I guess, I've overworked myself during the rehearsal last night.
I rather believe that it was only a muscle spasm than a heart attack or asthma.
I wanted it to go away.
I don't want to go through the pain ever again.


[source from Wikipedia]