My pinky keeps going numb. why is it?

Nerve problem: As long as you aren't having a change in color of this finger it is probably a problem with a nerve such as the ulnar nerve (sometimes referred to as the funny bone). This can happen after injury to this nerve at the elbow or from resting your elbow too much on an arm rest. To find out you might need to see a neurologist.

Many possibilities: Numbness can occur from various reasons. Some potential causes include vitamin deficiency, nerve damage, nerve compression, and alcohol over consumption, side effects of different medications, or as a result of different systemic medical conditions such as diabetes. Get evaluated by a professional to determine the diagnosis. Treatment is based on the diagnosis.