I'd like to join Gelati in welcoming you here, that reply contains some good advice.
I've only a couple of things to add. The first is that you are doing more good than you realize. Of course you do not know what to say, nobody does.
As an example a close family member lost their partner very early in life and rang me once or more every day from a remote location I could not go to. I would hear the phone ring and would feel so helpless. There was no 'fix-it' phrases or solutions.
I'd listen, sympathize and try to steer the conversation towards happier thoughts, old times that had been enjoyable, pets, movies we has seen, anything. I stocked up on (not particularly PC) jokes and scattered them though the conversation. Eventually the call would end - until the next time.
I've never felt more useless.
Years later that person told me I'd made a huge difference, all the difference in the world.
I'm not saying use anything I did, except maybe try to conjure up happy scenes from the past. Trying to use logic and persuasion did not work for me.
You are doing more good than that 'well known help line' at the moment.
Medications react differently on different people, this excessive fear may well be that this is simply a symptom of the meds getting up to speed, and having side effects on the way. I'm glad the doctor has been contacted and is aware of the situation.
I remember how much pressure this was on me, and you will be under the same, so can I ask who is there to support you? You need it too. I had my partner, and it made life a lot easier. I'd also suggest seeing your own GP, partly for advice, partly to monitor your own health at this time.
Please feel free to talk here anytime, let us know how you go