I find it unfortunate that according to your banner, after the time you have away from smoking that you'd even CONSIDER it, even "occasionally". As others have stated, if vaping is no good for you, then you can quadruple that and apply it to smoking even "occasionally". Of course that's barring your even ABLE to smoke "occasionally". I have found there to be very FEW who fall into the camp of an "occasional" smoker, which by the way, what does that even mean??? To me "occasionally" would be maybe one or two every few months or so, much like the way I drink. Of course, I might go 6 months or more without drinking also. With smoking however, most find that while initially they may be able to smoke one here and there, over time the amount they smoke increases as tolerance builds and dependency occurs. If you smoked more then that in the past, chances are GREAT, that you will return to whatever amount you previously smoked.
I don't think ANYONE can really advise you properly on this thread, as most will not only be unqualified, nor have you given enough information for anyone to even really speculate properly, what could have been the cause for your symptoms. Given what you have said though it makes me wonder, how much you smoked, and for how long. How much you vaped, what strength, duration, brands, quality, PG/VG mixes. Unless even one of those doctors questioned you extensively about your vaping history, and your health history in general, I can say WITHOUT A DOUBT, as a medical professional, that their "medical" OPINION means NOTHING! Without proper testing, of which there currently would be FEW to even narrow down a culprit, stating that "vaping" is the cause unequivocally, would be wrong! They could say, try to stop vaping ALONG with everything and if the ........ stops, and your health improves, MAYBE it was the suspect, but again, with ALL the variations you have from "vendor" to "vendor", with some people literally mixing stuff up in their sink and bathtub to state of the art labs, this would be darn near IMPOSSIBLE to pinpoint!
ANYONE can mix up some "juice" and "hang a shingle" out on their doorway to the WIDE world web, and call themselves a PREMIUM, and QUALITY e-juice supplier, doesn't make it so though! There are also an ASSORTMENT of flavoring that could be causing the problem, whether you "vape" them, or consumed them in substantial quantities! As someone else mentioned, you may be consuming too much nicotine. I know for myself, I can't consume the same amount of liquid that has 24 mg WTA, added to my 18 mg/Nic in small amounts, without getting ill. However without it I can "chain vape" all day and be just fine!
Pardon me, but it sounds like you've already made up your mind. Part of me wonders if the addiction to smoking as a whole isn't complicating the issue and contributing to your decision. It just seems like if it were me and I had that much time, as I only have a couple of weeks if that myself, but if I had your time and TRULY wanted to stay off cigarettes, I wouldn't be so quick to go back to them, or give up vaping, and would DEMAND more specific answers! Unless there's A LOT more to what you're sharing, they haven't really told you ANYTHING of consequence AT ALL! I sure hope you haven't invested the amount I have into vaping gear as well! Either way, I hope you get it sorted out! Best of luck, and we'll still be here, or hopefully so, ECF will I'm sure, if and when you figure out that smoking isn't the answer...