What Causes Persistent Pain In My Arm?

Hi I am a 21 year old female. I have been experiencing severe pain in my left arm all week, particulary when sleeping and moving it. The pain started when I woke up with a stiff neck one morning. The pain is felt in my shoulder as well. I have also noticed for the past few days, the tip of my left thumb has turned numb and wont return to normal. It hurts when i push it against anything or apply pressure to it. This numbness has started to occur on my left index finger aswell today. What could be the cause. I also suffer from raynauds in my hands and feet and get chronic knee pain (chondromalacia patellae) I am about 5ft 3 and a half and weigh 7.5stones.