You are not alone on this one. I have the same fear of new meds. I too look up all the side effects and freak myself out. I recently switched from Lexapro to Effexor and was terrified to do that. The switch went okay although I don't like Effexor and am now switching to Zoloft. I just took my first one today. I had myself so worked up about it that I had to take Ativan in the middle of the night. But I had to bite the bullet and take it. I need to find some relief from this terrible anxiety. I also recently took a round of antibiotics for strep and was scared to take them but I did and it was fine. You will be fine too. Like I said, with meds sometimes you just have to bite the bullet.
Your fears are actually quite reasonable. Many medications, especially those prescribed for psychiatric conditions are "mystery meat". If you research them you find "mechanism of action unknown".
As far as anxiety goes the only medication I would take is valium, which had a splendid safety history, but recently has been targeted by the drug enforcement agency.
I'm pretty scared of taking pills to, that's why I prefer something more natural like cbd oil.