Ok what you are describing is known in the British Army as Combat perception, It normally happens to soldiers who have seen long hard campaigns. From what little I have been told about it is this:
It comes from our evolutionary flight or fight response, when we where apes we subconsciously listened for environmental keys that we where about to become lunch for some large hairy beast, the best example of this is when you are walking on your own through a deserted wood an nobody is around a twig snaps you instantly get ready to Fight or run your legs bend because you might have to run an you ball your fists ready to fight.
This ability is adaptable a soldier who has seen a lot of combat will react quicker to a dangerous situation subconsciously they are on the look out for signs that they are in danger, I have seen soldiers duck right before a hidden enemy opens fire if you ask them why they ducked they will tell you that something felt wrong or they felt that they where in danger. I myself when walking down the street stopping an double checking that the item at the side of the road is not a IED (6 months in bazra teaches you anything can be turned into a bomb).
So don't be worried that you have some form of ESP or your the next Mystic Meg its perfectly natural for you to notice things that are odd or you have a feeling that something is going to go wrong is millions of years of evolution that's telling you something is amiss.