Mechanic Job in Blacklick, Ohio

I have a 2001 Oldsmobile Aurora-last weekend (week ago) as I was driving I started losing power-security indicator along with other indicators were showing up on the dash. As I was driving I noticed I was losing power, lights going dim, my car cut off just before I reached my house, I went back to jump start the car and it started up, just enough to get home and then it cut off in the driveway. It didn't start again. At this time I thought it was the battery, bought a battery-no start; I thought it was the starter-still no start. I then had the security system and the key of the car re-programmed-still no start. So, at this point I'm thinking it's the alternator...I'm not a mechanic but I'm all out of reasons. I'm hoping y'all can help me. Thanks!