What Causes Red Bump On The Top Of Head?

I have a small red bump (about 4cm wide) on the top of my head. It is very tender to the touch and leaking clear fluid. If I do touch it, I feel dizzy, especially so if I touch it too hard or push on it. In those cases, I have to sit down for a few moments to get my self settled. I have had a cyst removed many years ago from my scalp and have had more pop up over the years. They are slight tender but do not cause enough problems to do anything about. This small red one bump is very different and obviously presents very differently. Do you have any suggestions on what this could be?