Hello Kirstylw!
I have indeed changed antidepressants a few times during the last four years, but I haven't had any bad side effects. I think that it depends on each one. Surely having to go down to 10 mg. before switching to duloxetine may be quite hectic if you somehow already feel sick. Please take it easy on you these days and try to have plenty of rest .... if you really so bad don't think it twice to call your doctor as you may be asked to take something to ease the symptoms ..... then once you start on duloxetine which is an SNRI, meaning it will work both on serotonin and noradrenaline, you will probably feel better!
I have used duloxetine for a while as I was taking it to help me with migraines, but it was not the right one for me, especially in preventing migraines.
When I had to change meds I was really frightened reading some experiences of other people on the web ..... but then it turned better for me as the next med was a fine-tuning of the previous one or because it was not working for me.
So let's hope this fine-tuning for you will work positively!! These days you will be in my thoughts so do write if it helps you to feel better!!