Sounds like you have a parasitic drain i have left my car with a fully charged good battery for a month with no issues.
After each time your battery goes flat you need to charge it overnight, it will never recover enough just driving around and dont rule out a bad battery even if it is new it does happen.
I've attached a video to show you how to test for parasitic draw and how to diagnose whats causing it, it's pretty much the same for any car, oh and a good multi meter will have a fuse to stop damage to the multi meter unlike the one he's using LOL