You're definitely not a moron. I'm surprised she wasn't familiar with using ADs to treat the symptoms of IBS. I'm in the US (Oregon) and years ago I was prescribed ADs by my doctor, so I don't think you need to say you're depressed to get your refill.
I'm really sorry you're having to go through all this. I hope you find a more knowledgeable and sympathetic doctor soon. ***HUGS!***