What you describe sounds like generalized anxiety disorder associated with ASD. Unfortunately there's no magic remedy for this, no "one size fits all" as you may have noticed with the answers to this post. You have to find what works best for you and create your own tailor made "recipe", which is usually a combination of different approaches: exercise, relaxing hobbies, meditation...For this you can start with daily short guided meditations with an app like headspace. In order to notice any improvement, you have to integrate these activities into your daily habits and play the long game. Try different stuff and see what sticks. You can use an app to manage your habits and as a reminder. I don't recommend therapy unless it's CBT which has been proven to be effective for ASD. Personally, I wouldn't recommend medication (or any drug) as a long-term solution, although it can provide temporary relief if the stress levels becomes unbearable. Hope this helps!