Battery problem?? Tailgate problem??

[Jimmymac148]

I recently had to replace my battery after my Mrs left a parking light on that completely drained it . I fitted a Yuasa silver battery that was recommended for my car (X5 3.0 2005 ) . All was ok for about 6 weeks then if the car was left for a day it doesnt have enough power to turn the engine over ? Any ideas what could be draining the battery ?
I also have an intermittent issue with the tailgate popping open ? Tends to happen more in damp/wet weather and will do it 4or5 times nearly every time I open the doors ? Any help will be appreciated .
Ps ive had the alternator checked and is reading over 14amps