Recently ive spent a lot of time on my phone on facetime etc and today (after a long facetime call last night) i have had numbness in my thumb and forearm. what could be causing this? is dvt a possibility from being immobile for 4 or 5 hours?

Cubital tunnel : DVT is caused by a clot in one of the deep veins of your extremities. They are much more common in the legs and are accompanied by discoloration, pain and swelling. More likely you have cubital tunnel syndrome, where the ulnar nerve gets compressed while traveling through the cubital tunnel in your elbow. This can happen when your arm is bent for long periods of time. Keep your arm straight.