What Causes Sudden Palpitaion And Shortness Of Breath After Smoking With History Of Anxiety And Bulimia?

Hi there, I've been a regular smoker (about 5-7 per day, 10-12 on weekends) for about a year now. I am a 20 year old female and have previously suffered from anxiety, depression, bulimia and anorexia. Most of that is behind me, although I do still suffer from anxiety and about once every 3 months I have difficulty catching my breath (even before smoking)- I have been given inhalers for this in the past but as it is anxiety related they haven't helped for more than a few minutes. Over the Christmas period I smoked more, drank more, did very little exercise (for the past 4 months I have been swimming/running/rock climbing about 4 times a week, previously I had a year of little physical activity, and the year before that I overexercised and ran about 6 miles a day 5 times a week). My issue is that today with each cigarette I have had, I've experienced a visibly increased heart rate (I can see it pumping through my clothes) as well as some slight stinging in the right side of my chest near the breastbone, and the shortness of breath which I regularly experience. The logical solution is of course to stop smoking, which I have designs to do, but I am wondering why this increased heart rate in particular is occuring now, and has never done so before. I should mention that I had a relatively inactive day, then went for 15 minute jog. The result of smoking was the same before and after the run.