99 cadillac deville issues!! electrical/alternator?/?

[Danielle]

Im having issues w/ my 99 cadillac deville.. My battery was dead one day, we jumped it, and was dead the next morning, jumped it again and the same thing.. So we went to autozone and they said my i had an old battery so we got a new battery, and about an hour later i went to my car unlocked the doors and my alarm started going off and tryed started my car and it was dead.. the lights and radio came on.. before i was having this problems i would notice my trunk would pop open at times, and the gas gastic door would pop open as well.. HELP