Battery problems

Well, you have a drain somewhere and they can be hard to find.
Something is drawing current when it souldn't.
What about the radiatior cooling fan. Can you hear it run? And are you sure it is not sticking on? Shut car off at night and look around inside and out for lights and sounds. Brake lights can stick on.
Glove box light will drain a batt in about 36-48 hrs.

You can get an idea of how big the drain is by how long it takes to make it weak to crank/ start.
A fan, or tail lights can drain it in just a few hours. A dome or glove box light or radio will take a day or more.

Has anything been serviced or done to care before this started happening? Stereo. Add on lights. Etc?

After buying your last battery, you may have let the car sit too long without recharging it or not recharging long enough. Many battery manufacturers recommend that, if you know the car will sit for a long period, put a charger on the battery or run the car engine at least once a week. Maintenance and battery usage are the key to a long lasting battery. When a battery sits for a long time, sulfation will begin to develop on one of the internal plates, thus gradually decreasing battery voltage. Sulfation is like rust. It will spread over a period of time. The longer the car sits. The more sulfation spreads. And the longer you will have to recharge the battery. Aside from that, all cars have a parasitic drain from our accessories, air condition, heater, power windows, locks, alarms. Anything that draws power from the battery. This drain occurs when the car is turned completely off. Try upgrading your next battery and focus on a higher Cold Cranking Amp rating and higher Reserve Capacity Rating. When you upgrade your battery ask for a battery/charging and starter test, this will tell you if you have a charging system problem or just a bad battery. This test is free at any battery retail shop.