Severe knee pain, swelling, tenderness, etc?

I've recently been having extremely severe knee pain lately. It's located in my left knee on the left side all around my knee. It hurts to walk, stand and even just laying still resting. It's always swollen even when I wake up in the morning it is swollen. My knee gives out on me and it's warm to the touch. It also looks weird and there is a spot on the left side of my knee that is tender to the touch. I hyperextended my knee playing basketball in middle school and had to wear a knee brace to keep it stabilized. About a year ago I was dropped on the same knee and the pain started back. Recently I have hit my knee on the side on tables or fallen on it because it's very unstable and the pain has gotten so bad over the last few days that I am going to go to an ER or a walk in treatment center tomorrow to get it fixed. I'm in pain all day everyday. I recently worked as a cashier for about a year and now I work in a call center. I also walk about 3-4 blocks to get from my car to the building I work in also. Not sure if these could be things that are affecting my knee. I did a symptom check on webMD to see what possible injuries I could have and so far I've gotten ACL and PCL tears, meniscus tear, dislocated knee, repetitive motion injury, bursitis, stress fractures, gout and tendinitis. Any idea what could be going on or what I can do to get through tonight and tomorrow at work until I can get to a doctor? And should I go to an ER or should a regular walk in treatment center with x-ray capabilities be fine. Thanks a lot.