Hoping that you are benefiting from some well-deserved ZZZs, Kate. Sleep deprivation absolutely messes with our emotional and physical equilibrium as well as our judgement. Do what's needed to get a couple of nights under your belt. I, too, suffer from insomnia. I haven't found any magic solutions, but avoiding sugar and caffeine after 1 pm, 1/2 a unisom an hour before bed, practicing good sleep hygiene (especially around screen time), and audiobooks (both to drown out tinnitus and soothe/distract me while awake) keep me out of the red zone most of the time. Definitely talk to your doctor.
You know in your heart that smoking would NOT help you sleep, would harm your mental and emotional wellbeing, and would trigger its own shame and despair cycle. You've shut the door on all that, for good reason. Keep it shut, dear. COVID may have been your final tipping point, but there are probably 100 additional reasons that you've STAYED quit. If those reasons start to get hazy when you're coping with a bipolar swing, right them down on paper in big, bold, print, and read them aloud. I've resorted to that a few times.
Please take good care and keep us posted on how you're doing. You have a team of supporters here on the Train who have faith in you and are here to support you, just like you've supported so many of us. Sending you love and fortitude.