2003 Chevy Venture wont start..PLEASE HELP!

I have a 2003 chevy venture...yesterday I went to start it and it acted like the battery was dead, but it still started. Then today, it wouldn't start at all. So I jumped it and it started. Took it to the store, and it wouldn't start again. So once again had to jump it. I brought it home and let it run for like 30 minutes. I went back out there and on the little screen it was saying security...turned it off and it wouldn't start again. But this time there was no clicking or anything. What could this be??? Please help, I cant afford to take it to the shop.:frown:

turn the headlights on and see if they come on nice and bright, if they do your battery is fine and it might be a issue with your security system or starter. sounds like your battery is not charging, i would suspect the charging system/alternetor myself. if you take it off or jump it again and it starts you can drive it to your local parts store and most can check to see if the charging system is working