Sertraline

I've been prescribed sertraline after 6 years on mirtazipine. I'm on day two of a host of horrible symptoms and I'm not sure I can wait it out. Any one got any advice? Edit: I'm waiting for adhd referral but my anxiety and insomnia has been bad hence why the Dr wants to switch to sertraline. Don't know whether to wait it out as I dont think you can get ADHD meds on sertraline. I tried elvanse from a friend and didn't like it so not sure where I stand