Arm pain, swelling, rash, bruises on arm. Normal ultrasound. What to do?

my left arm was hurting on saturday night and it started to swell and had like a rash on it. I went to bed and woke up with one bruise on my arm, in the morning you could watch the bruises pop up, I went to the er and they said it was cellulitis . I went to my dr and he said it wasnt, but he didnt know what it was, well 2 nights later I had such a sharp pain, it felt like the arm was getting cut off and another big bruise just popped up, it is now really sore and feels tingly, I went back to my dr today, he sent me back to get another ultrasound, the 2nd one this week to check for a blood clot. it is normal. I am so sore and dont know what to do, can you give me some ideas?