What Causes Severe Pain And Throbbing In The Arm?

Hi, I am a college student so I'm pretty young and I've never had any serious medical issues before. I am a woman, age 20, 5"2', 105 lbs. Before I went to bed last night, I noticed my right arm aching just a little bit, enough to make it difficult to fall asleep. I finally fell asleep but woke up 3 hours later with a stronger aching, throbbing, and weakness in my arm. It is mostly my upper arm and around the elbow area but it also extends into my wrist and forearm. Mostly it just feels weak and achy. And it makes it difficult to fall asleep and focus on anything else. Strong throbbing. I can still use my right arm it just continually aches.