Yep. I had the same issue after I started
vaping. What it turned out for me, was my body adjusting to NOT dealing with smoke.
I mentioned it to my local proprietor of vape stuff, when it happened to me and he giggled and asked me if I ever tried to quit smoking previously. Which I had. Then he asked "Do you remember the coughing, the tightness in your chest, etc.?" Which then I did remember going through that and I said "Yea... now that you mention it." That's when it hit me that I was going through. He recommended using both old analog cigs and
vaping, and slowly weaning off the analogs (he went through the same thing) but not going cold turkey off the analogs. He also recommended getting rid of the tobacco flavored juice and find something that isn't remotely close to tobacco flavor.
I took his advice and in a couple of weeks I was completely off analog cigarettes and 100% e-cig without issues this time.
I still bum an analog from someone just to remind me that those things REALLY SUCK. Especially since I vape a nice flavor. Cigarettes just taste awful in comparison.