It could possibly be a problem with the alternator not charging adequately if you say the battery was replaced a few months ago, presumably with a brand new one?
There could also be something in the car that's permanently draining the battery, e.g. a bulb in a concealed compartment that isn't turning off as it should.
It really needs someone to start taking a few measurements in order to determine what's happening. As you say you're not technical I won't bother to say what they are, except to say I think you will need to visit a garage or auto-electrician.
Edited by Galaxy on 19/02/2015 at 19:50
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