I've just got back in from doing the 2nd run of week 5, after going backwards a bit due to back pain a couple of weeks ago. When I started the 8 minute run, my head started to pound as if it was going to explode! It calmed down when I walked and then started up even worse on the second 8 minute run. I've just taken pain killers with a pint of water and have done some stretches and it's much easier.
Has anyone else experienced this? What am I doing wrong? I thought it would get easier, but I feel like I'm falling apart!