Anxiety is winning.

I've had stress and anxiety my whole life, but recently it's been worse. Few months ago (last October) my mental health hit rock bottom basically. I almost ODd, and then got diagnosed with major depressive disorder with severe anxiety. I know what my major triggers are and I know depression pokes its head only when I can't keep my anxiety under control. I was doing so good up until this week. I don't know what happened but something triggered my anxiety and now the past memories are hunting me, and I can't stop any of it. It's too loud and chaotic in my head for me to calm down and I've been crying for the most part since yesterday. I was doing so good and now it feels like I'm back to the bottom. Anxiety is in control of my mind and I don't know how to stop it. How do I stop it?