Question about ECigs!!!! Help??

Okay, so I know that any smoking at all is bad while trying to concieve, I have never been addicted to smoking, I've smoked off and on for the last 6 years. When I say off and on, I mean that I could smoke one pack in a day, and then not smoke again-or even want to-for MONTHS. However, I recently bought an ecig because I'm just someone who enjoys the look of smoke and playing with it, for photography purposes. But I'm curious, I don't know how to log it, since it isn't a real cigarette, but does have nicotine, I am confused as to "how many" cigarettes I'd need to log. So, let's just say I take 15 drags a day, how many cigs do you think that's equal? 1? 2? 3? It's driving me crazy! I don't want to ruin anything. Please share your thoughts. I know it's a lot to read, but please.