I think you still may be dehydrated and not only this but your electrolytes will be out of balance and this will make it worse. The situation would be improved if you drank an isotonic sports drink (such as Lucozade
Sport, Gastorade/ Powerade) or mixed a rehydration sachet (such as Diorralyte) with the water then that may help.
Really though, it is also likely to do with the lack of food that your bodies got and therefore the reduction in energy. As well as that the muscles around you neck may also be quite tight which can also induce headaches (as well as the change in blood pressure and also oxygen levels in your brain when purging though this should only last for a very short length of time). Really for those there isn't much you can do apart from trying to at least reduce the amount you're B/Ping and also, as it has increased recently then getting help behind the emotional issues surrounding this may help as it's likely something recently has caused this. If you contact the supporters via live help (if they're online and available on there) or contact them on
support@recoveryourlife.com then they may be able to help you with the reasons behind this and therefore make it easier to at least reduce the amount you're purging, if not stop.
