Your symptoms sound quite concerning. Numbness over that large area of your arm should be evaluated by a physician right away. Numbness in limb with no other symptom is usually due to some sort of problem with the nerves that service the arm. Numbness as an isolated symptom is usually not due to a blood clot. A blood clot in the veins of the arm is more likely to cause pain and swelling than numbness. A blood clot in the arteries of the arm would be more likely to cause pain, numbness, and weakness in the arm. Thus, I think your problem is more likely to be caused by something else.
I suggest that you schedule an appointment with your primary care physician
. He or she can take a more detailed history of your symptoms and perform a comprehensive neurological exam. In addition, your doctor
can order any necessary imaging studies that may help to figure out why you developed this numbness. It is possible that you may need an MRI, though I can't tell for sure. It is also possible that if your doctor finds a neurologic deficit, that you may need referral to see a neurologist
for further testing. I hope that answer helped.