I second NewDawn's suggestion that you try mindfullness therapy. I took a mindfullness-based stress reduction course almost years ago, and it literally changed my life.
With practice, it will help you manage your thoughts, emotions, and physical sensations in a less judgemental way. I really think it can help with irritability and brooding thoughts as it allows you to accept them and accept yourself without changing things or making things perfect. With an open mind, you'll feel more relaxed and at ease with yourself/
Do a google search to see if there are any mindfullness courses in your area...there's a chance that it will make you more calmer and focused in the long run. Best of luck. 
_________________
Given a “tentative” diagnosis as a child as I needed services at school for what was later correctly discovered to be a major anxiety disorder.
This misdiagnosis caused me significant stress, which lessened upon finding out the truth about myself from my current and past long-term therapists - that I am an anxious and highly sensitive person but do not have an autism spectrum disorder.
My diagnoses - social anxiety disorder and obsessive-compulsive disorder.
I’m no longer involved with the ASD world.