Your EVOD is fine... your nicotine level is most likely the issue. If you smoked anywhere near a pack a day, 18mg will be the bare minimum you'll require to get through the craving times (morning, before bed, after meals, etc.). If you smoked more than a pack a day, it would not hurt to try 24mg juices too...
Nicotine is NOT the problem, so don't feel bad if you have to have higher levels to fight through the cravings!
Also, using a higher VG% juice will produce more vapor, which many people find to also ease the transition, because you get the sensation of smoking (thicker vapor production). Higher VG will also reduce the throat hit (TH), so your draw will not be as "harsh".... this is a good thing for higher nicotine levels.