Sertraline - first day taking it?

Hi, emily!
You are not alone... I think everybody on these forums can emphasize with you about starting a journey with a new medication. It's scary but you'll get through it although there may be some bumps along the way.
Some things to keep in mind about side effects are that the vast majority of users experience few if any side effects and if they do they're usually mild and transient. Most resolve within just days to a week or so and generally can be managed with OTC products recommended by your pharmacist.
You'll read horror stories from the folks who've had problems but you won't hear too much from the tens of thousands of users who are living happy and fulfilling lives.
You've already taken a giant step in reaching out for help... it's a brave thing to do. Just remember that your doctor is your friend and so is your pharmacist. Stay in touch with them throughout this initial period and you can post here with any questions or concerns you may have. We're not professionals but we're happy to share information and our own experiences.