Help! My car won't start

I have a 2001 Pontiac Grand Am with 78,000 KM on it and Yesterday I came out from work (after driving it in the morning) went to start it and it won't start. It is turning over and wants to catch yet it is not catching. It seems to get a bit of gas but just not enough. I have listened by the gas tank and the fuel pump seems to be working, I disconnected the battery for 15 minutes or so (to try to reset the computer), and a couple of other things. Could you please let me know what else I can check. I am not the most knowledgeable about cars and I have worn out all my ideas (didn't actually take too long). Any kinda help you could be would be great. I know that these cars have a security feature on them and the security light does come on when I put in key and turn it to acc. Or even to "on". I would just like to try everything before I take it to a mechanic.