It will be due to coming off your medication.
From my perspecitve, you are coming off too quickly.
To go from 30 to 15 for only a week is a hell of a drop, in my view you should have gone to 20 mg for two weeks, then 15, for two weeks, then 10, 5, and down to zero.
However, I bow to your GP's medical knowledge, although not his personal experience, which I believe, in thnis instance, has the edge.
For what it's worth, your side-effects will abate, but you may have to 'cold turkey' through them, which again in my opinion is far from helpful in your condition, especially when you will have top adapt to your new medication and wait for their side-effects to settle - p[robably two to three weeks.
See your GP and ask him if maybe you should be coming off more gently than this? He will probably argue, but I do speak from experience, and he probably doesn't, so in this instance, i do know what I'm talking about.
See what he says, and post back.