How can I help my anxiety?

Ive stayed up every night balling my eyes out for the past like 4 days bc my anxiety has been off the charts. I am having a really hard time managing it.

I have been recently accepted into college and am really worried about my relationship. Me and my bf have been together for over 3 years. We do want to stay together throughout college and afterwards. He has never done anything throughout our relationship to ever make me doubt him or not trust him. Like literally nothing. But I still find myself imagining him cheating on me and things like that if we go to different schools.

He assures me he won’t and I do believe he wouldn’t, but my mind keeps making up scenarios where he does and I can’t stop them. I do have a diagnosed anxiety disorder but it is getting worse as I get closer to college.

I don’t have anyone to talk to about this bc nobody I know understands what it’s like to be with someone for so long approaching college.

Any advice is appreciated.