What Causes Feeling Of Lump And Bruise In The Right Armpit?

One week ago I woke up with pain and swelling in my right armpit. When I would put my arm down it felt like I was squeezing a ball in there or something. Two days later the pain started moving down along the inside of my arm and by that evening it was 3 quarters of the way down the inside of my arm. It was so tender I could not bring my arm down to my side or touch it. There was no bruising though. By the third day I could not reach with my arm without it feeling like it was being ripped apart at the bicep and also just below the inside of my elbow. The lump feeling in my armpit started subsiding but the pain and tenderness in the armpit was still there. After 5 days I went to the ER and they did an ultrasound to look for a blood clot. None was found. On the 6th day my arm started bruising from my armpit down, following the path of my basilik vein. I am even bruised on my palm where the vein works its way down. I am still very tender, my arm still feels like it s being ripped apart if I try to straighten it or reach for anything. I have not injured or had any trauma to my arm. Any ideas? The ER Doctor had no idea what it could be.