I sympathize. I, and many of my friends from my college years, fit that description really well.
I emphatically urge you to get a handle on this ASAP. I'm 37 and I have friends my age with severe health problems because of life stress and poor habits.
You've done a great thing to quit the stimulants. Now go find yourself a yoga studio or some Tai Chi classes. Practice 2 or 3 times a week.
Walk outside every day. Get out to the woods or the water if you can.
Do a minute of deep breathing every hour. Some people call this meditation, but you don't have to think of it that way. Just take deep breaths all the way down into your stomach and exhale fully.
None of this is rocket science, but it honestly could save your life.
Best of luck in your endeavors.