my bum hurts

Like my email said, I had a wedding on Saturday, and managed to really hurt myself while drunk on a bouncy castle, so I haven't done anything for the last 5 days or so. Can't really remember before that, definitely did a couple of 30min @21, 7550 and 7650 ish. Havent really improved at all since I started training, which is pretty annoying. Also, is anyone else losing about 2litres of fluid to sweat each time they erg? I seem to be losing 2kg between going to the gym and coming back, and had headaches a few times as well, which is worrying. I didn't have this trouble at easter, so i dunno whether its just because its warmer, but I doubt it.