I would agree with BoeingBoy, to be concerned about the dangers of flying is essential, to lose sleep over them is bordering on aerophobia. A very common condition of course but not really one that is compatible with being a pilot. However, don't worry as it is also very treatable. Release, do you fly a lot as a passenger? If not it may be an idea to fly a bit on a big jet just to get used to the feel of it. Personally I don't think about the potential for all the fuel in the tanks to ignite in mid-air, but I have to admit I sometimes get a little nervous in IMC conditions in UK airspace, although we have the best ATCers in the world we also have the busiest airspace and only luck has prevented the 'nightmare scenario' from happening thus far.
What has already been said is very true, it's just like worrying about your car getting broadsided at a road junction and you being seriously injured or killed. Which is of course a far more likely happening than any aircraft accident, particularly when flying with a Western airline.
The way to get over a phobia is to introduce yourself to your fear gradually, and since your worries seem to centre around the fuel tanks, try flying a bit as a passenger on jets and you will soon realise that the potential for something to go wrong is minimal. In GA however, things can go wrong sadly and it seems that at the moment not a weekend passes without news of a serious GA accident in the UK.
What is really not worth worrying about however, are the consequences for you in a serious accident. As BoeingBoy says, I don't think you would feel much, and as for me, if my number was called while I was in the air, I wouldn't really want to go any other way.........