As the others have said, Louise, ketosis is nothing to worry about. I felt crap with a bad headache for about 3 days, but then it lifted and I felt absolutely fine - in fact, probably better than fine!
I was worried sick that I'd end up with the headache again during my PP days on Conso - but, thankfully, this hasn't happened.
I'd never heard of ketosis until I came onto this forum. I just figured that the headache was part of the withdrawal/detox process.