@Lisa Sullivan . The mod you have is ok to use Smok don't have the best rep but here's what to do, you could do with buying a MTL tank. Aspire Nautilus is probably a good choice even though the first version is getting old it still vapes great. You would now just need to buy some 12mg Liquid if it isn't giving you enough up the 12 to 18mg.
So you sound ready, you had an issue last attempt but this time You can help yourself. So as said above spend your tobacco money for the next week, month etc depending on when you next get payed on a MTL tank and the remainder on juice and spare coils. Now you have removed the money you would have wasted on smoking, DO NOT allow yourself to break into money for living and savings. Now you have to vape to remove the cravings, those cravings will be the worst for say a week, after a week you will be feeling a little better and after a month you may well want to lower your Nic level again. All those other chemicals that mix with nicotine in tobacco smoke well they are addictive but not like nicotine and they make the nicotine even more addictive, once you get rid of all those chemicals you will still crave but no where near as much as at the start.
A MTL tank will use far less eliquid but you will be taking a drag like smoking, not that big hit you where getting with a sub ohm tank like the ones by Smok. Due to a MTL drag being shortish and creating less vapour this is why it is used with higher Nicotine levels, But you could also use Nic Salts eliquid this is available in 20mg but it's a way smoother hit and faster to work than standard nicotine.
You can always go back to sub ohm vaping once you are ready to try again but get the first month or 2 out the way, and lower the strength to 3mg for a similar hit to higher strength. You learn as you go, but please follow the advice about spending your tobacco money on a MTL tank and coils and juice. I did it this way and i was a heavy weed smoker for almost 30 years. Almost 6 years ago now but i did carry on spending my tobacco money on vape gear, Now i look at what i own and think that money would have gone in the ashtray. Good luck with the next go, you can do it.