Hang on there...yes, the nic level might well be a part of the solution, but no one's asked what gear you're using!!
There's a huge difference in how nicotine hits you between using something like an "ego" battery with a clearomizer, and using something at low resistance and high watts.
MANY people quit cigs by starting at 18 or even 24 mg liquid when using a clearomizer or other device that might be 2 or more ohms.
MANY people end up vaping more powerful devices, that can run 30, 40, or more watts, with resistance under 1 ohm - and they usually do that with 6mg or less nicotine.
SO - what kind of equipment are you using?
If it's a "pen" style of any sort, you very likely want more nicotine. If you started right off with a "subtank" kind of thing, then that's not the problem - 6 should be OK, and you might need to vape more or vape less, depending on your symptoms!
Final tips, just to keep confusing you...
1 - most of us who quit will say, "you can't vape too much. vape as much as you need to not smoke. puff, puff, puff, it's OK".
2 - nic can keep you awake! If you ARE chain-vaping, that might be part of it - it's a stimulant. Just seems unlikely that's what's happening if you're using 6mg though - unless you're like drinking it...
3 - YOU CAN QUIT. THousands of us did. (For me, honestly, it was stupid-easy, I wasn't even trying.)
I'm new to vaping. I quit smoking two days ago and switched to vaping. My question is when do the withdrawals get better? I don't have headaches but I'm moody and tired all the time and when I try to sleep I just lay there forever. Thanks everyone