Everytime I have my elbow bent my fingers and hand get numb is there any reason for that?

Nerve or vascuinsuf. Either median or ulner or both nerves are compressed at elbow or brachial artery is compressed. All need to be investigated.
Cubital tunnel. The most common cause at the elbow is cubital tunnel syndrome. The ulnar nerve (crazy bone nerve) passes behind the medial epicondyle (inside bony prominence) then underneath the ligament of osborne. Flexion tightens both the posterior ligament underneath and the ligament of osborne over the nerve compressing it. This causes numbness mainly in the ring and small fingers.