This only started happening recently and has only happened twice so far - once last week and once on friday.
Both times it's happened it's been during P.E and I'm running at the time, and I feel a tiny bit of pressure in the top back left area of my head, then I hear a small popping sound (it's hard to describe). Then, the area around where the 'pop' happens (I can feel it), it feels warm around the area. It's like someone poured warm water on that part of my head - sort of. When it first happened, I felt my head 'cos I thought I was bleeding, but there was nothing, same with the second time. The warmness fades away after a mionute or so.
Anyone got any idea of what's happening.