Malang is a song from the film Dhoom 3. The singer is Siddharth Mahadevan accompanied by Shilpa Rao.
Malang is a proper word to convey an emotion associated with being love struck. Other English translations that convey the same emotion are besotted, lovesick, dumbstruck, and gaga.
Such a person would not know what day it was, what time it was, or where he was.
This emotion is a cross-cultural phenomenon, and therefore there are many words for it. You could expect this word to be used by people in India and find variations of it all over the Persian continent.
Malang could also be used to describe a person who exhibits the symptoms of being in love. The classic symptoms are being unaware of their surroundings, lack of concentration, appearing to be dopey.
ishq hai malang mera indicates that malang can be a possessive as well, however he is saying that the emotion -- or the condition -- called malang that he feels is due to love (ishq) :-)
Back pain is no joke...
It is an interesting song. I heard it once on the radio and it sounded like malam (back ointment).
The next time I lift something heavy, I'll be singing malam, malam dub malam malam, where the heck is that malam mera...