I've been having needle-like pain around my heart. Only happens when I lay on my left side, back, stomach. Comes in pulses. Happens almost every night.

Rib cage. A common cause of this type of positional,fleeting and often sharp pain is a pinched intercostal nerve or muscle that runs between two ribs. This is more of a nuisance rather than anything serious. See your physician if you have further concerns or persistent symptoms,however.