Ok, I appear to be overheating while running, its happened twice now this week and I really do hit a block. Thing is it comes on really quick, I get unstable and dizzy and really hot whilst sweating all over the place. First time happened after only 2 miles and took about a minute to kick in, second time I only got just past the mile! This is not normal for me and I don't appear to be dehydrated as I'm going to the loo all the time and its a clear colour. Any ideas?