Hi there, really sorry to hear you're having a hard time!
I was diagnosed with UC at 18 in 2013 and it completely freaked me out too. I'd never heard of UC before my diagnosis and from what the doctors told me I was convinced my normal life was over (I also have an anxiety disorder like you).
However, after overcoming my initial fear of all the new medication, it soon sunk in that this is just my 'new normal'... which once I reached remission wasn't much different to my life before UC. It was actually better considering I knew why I'd been feeling unwell for so long before.
You'll be okay. UC sucks, and there will be tough days, but you can absolutely live a normal life with this disease. You'll soon learn about
your UC and what foods/situations (if any) trigger it, and the medication will quickly become part of your daily routine.
Just do your best to relax, I know it's hard. This forum really helped me come to terms with my diagnosis, so just know that you're not alone. Good luck, I hope you feel better very soon