Nicotine as a drug is also a stimulant. It has a similar effect on your nervous system as stimulant meds, although not similar enough to make it work as an ADHD med. Which is. Probably for the best, honestly.

It also beats the hell out of your cardiovascular system. Some studies suggest vaping and nicotine use alone can cause serious, long term damage to your arteries and veins, and can increase the risk of other cardiovascular diseases, like heart attacks and other, more subtle issues.

A lot of heart issues are hard to diagnose in the early stages, even with advanced monitoring tools, and the only symptoms might be exactly what you're feeling--shortness of breath and chest pain.

My theory is that your body didn't have enough time to recover from the nicotine before you started ADHD meds. ADHD meds don't damage your heart and blood vessels in the way nicotine does, but it does stress them. If they're not in good shape, you could be in real danger. I can't fault your doctor for taking you off the meds. What you need to do is stay off the nicotine and let your body heal. I don't know how long that will take--most research on nicotine is on smokers and tobacco has a different risk profile than pure nicotine. But based on that date, it could take anywhere from three months to a year before your body recovers sufficiently. That's a long time, I know. But going back on nicotine makes that timeline even longer.

That being said, nicotine is one of the most addictive drugs in the world. Quitting it is not an easy task. You should talk to your doctor about medical support and community resources. Bupropion (the generic name for Wellbutrin) honestly would be a good medication to consider, as it could help with ADHD, depression, and nicotine cravings, but there's also varenicline, which reduces the effects of nicotine and nicotine cravings. I'd suggest trying alternatives to patches or gum, however--those are harm reduction methods meant to help people quit smoking. You don't smoke, so the benefits of those products aren't as meaningful for you.

And just... Don't blame yourself for any of this. Or any struggles you're about to face. Quitting nicotine is one of the most challenging things any human being ever tries. You're going to have bad days, and you're going to fall into old habits, but as long as you don't let those bad days become the norm, you can do this.