What is the reason behind my chest spasms at the height of my lungs?

Chest spasms. That's a difficult question to answer in this short space. I would recommend that you speak with your primary care physician or with a physician who specializes in lung disease.
Talk to your doctor. Do you mean spasms in the upper chest? If these feel like muscle twitches or spasms lasting a few seconds they are unlikely to reflect heart disease. If they feel like heart beats then they may be palpitations from extra heart beats. Please talk to your doctor about it.