It can take a while, it took me a few months to feel I had things right.
There's now an updated version of the article AlexTM referenced in the ECF Library at:
http://www.e-cigarette-forum.com/fo...ing-your-symptoms-while-adjusting-vaping.html
I'd take the palpitations as a fairly clear indicator of too much nicotine. Have you discovered a place to easily and cheaply get USP grade PG? Where I live it is easy to get by asking at a drugstore. If you're uncomfortable with the possibility of them asking why you want it, you can tell them it is for a fog machine. You can use this stuff to dilute any e-juice. Simple arithmetic will keep track of how strong it is, for example add 1/2 as much PG to a liquid to make it 2/3 as strong as it was. (1 / (1 + 1/2) = 2/3.) Shake it a bit to mix.
The headaches are a symptom which doesn't necessarily tell you much. They can happen from cigarette withdrawal and can happen from too much nicotine. Once you have your nicotine level right, if the headaches continue they may well indicate a need for something else which cigarettes were delivering.
For anyone reading this thread and wondering about "will I ever settle down", here's a description of the simple routine I finally settled into:
http://www.e-cigarette-forum.com/forum/tips-tricks/69830-settling-routine-long-term-vaping.html