remember what it's all about Caroline.You need to do whatever feels most enjoyable to you - even if you go back a week or two, or stretch a week over a fortnight. It's not community service, it's supposed to be life-enhancing. Get out and walk / run / skip / cycle/ swim/ join a dance class whatever that gives you a buzz , and gets your heart rate up for an hour or so, change the route, go with a friend, whatever even if that's off plan.
The plan will keep a week/ month whatever, and will be a lot easier when you're fitter and motivated again... 'retching' did you say.!!!well done you for sticking it so far.Do not let the plan make you feel like you've failed. it will have failed you if you end up losing the fitness bug for good