I feel paralyzed by my workload

I work as a project manager. One person on our team is working with another client, someone else has recently been fired. I’m used to a higher workload but I feel like I just can’t function or get anything significantly done, And the tasks continue to pile. I’m not burnt out I don’t think and I understand how we got into this position. But lack of organization for this amount of work is crushing me. How do you organize your workload and tasks? Especially if you have multiple things, projects, deadlines? What are some structures or mindsets that help you get things done even when your workload goes up unexpectedly. How do you keep yourself from stopping because there are just so many things to do. Side note: my wife wants me to test for ADHD. As far as I know I don’t have a family history. Apparently I’m showing many of the signs and she thinks that might be why my productivity is struggling so much. I’ve never thought of there being an additional issue, and there’s absolutely nothing wrong with people that do struggle with it. I criticize myself pretty harshly, I’m not discouraged, I just feel like I can do better. I just really don’t know how and I’m trying to figure out the best solution for me.