interior lights wont turn off/alarm lights keep flashing

[Abrown99]

We just got this car, had to replace the sump gaskets which fixed one issue.. Now when we close the doors (weather the car is locked or unlocked) the interior lights stay on..we have tried lockibg door with fob, with just key, as well as leaving it unlocked... The red alarm light flashes non stop unless we put the key in to start it... Then after a couple mins the outside lights start flashing.. I removed all interior bulbs so i wouldnt have a dead battery. But today its saying low voltage with a check engine light is on... Im so confused!! Could it be a dead battery cell??? Or the alarm its self??? Please any insite would be great...