I was in a rear end collision 4 days ago. I didn't feel anything that day so I went to the gym & did 40 minutes of walking/light jogging on the treadmill. The next day I went to work, but as the day progressed I started to get a headache. I then felt nauseous later that evening. I'm thinking I have a concussion. I've been resting the last 3 days. When I get up fast or turn around I feel like a bobblehead. I have slight ringing in my right ear. Is this a concussion?