What Causes Recurring Left Sided Sharp Chest Pain?

Hi. I m a 25 year old male of asian descent. I m 5 7 tall and weigh 70kg. I have this sporadic pain on my left lower chest for quite a long time now. I first noticed this pain when i was about 15 years old, i was riding my bike and suddenly it felt that I couldn t breathe like something is stabbing my left lower chest when i try to inhale. I can bare the pain, and it usually goes away when i exert more pressure breathing, with a little popping feeling inside. It also happens when I m just lying down doing nothing, i mean it s really sporadic. What could this be and how could i treat this? i quit smoking a year ago. I smoke and drink occasionally. Thank you very much.