One simple way to check if you have any draining of your battery is as follows:
Remove the negative battery wire.
Connect a test lamp between the negative battery terminal and the negative wire.
If the lamp lights up you've got a drain.
Next step, which is boring..., is to remove fuses one by one and check if test lamp goes out. Unless you suspect the alternator. If so, read the last paragraph.
Replace each fuse before removing next one.
When test lamp goes out, it means you've got a drain on that circuit.
Make sure you test all circuits.
If you still got light after all fuses have been removed, you're in for a bigger task, that normally means you have a drain on multiple circuits. So then the easiest way to find out where it is, is to remove all fuses and put them back in one by one. Make sure you put them back in at the correct position!
When the lamp lights up, note which fuse, pull it back out and continue with the rest. This way you should be able to register if there are several circuits that causes the drain.
By removing the negative cable and connect the test lamp, you may also find if you have a faulty alternator. This of course if you suspect so, ie. if the charging voltage is low. Then you remove the cabling from the alternator to see if the lamp goes out. If it does, it normally means you have a problem with your alternator. If it doesn't, it's back to the "fuse pull".
Hope this might help.