*What do you drink? What size are these 'bottles'? Any background information that would be helpful for responses (what exactly do you need to 'unwind' from!? Lots of people work, but not everyone drinks 2 bottles a week), etc.
I'm in my 20's also (25, will be 26 later this year) and between age 20-22 I drank just about as much as you say you do -- assuming we are talking about the same amount (in reference to 'bottles', how big is a bottle!?). I did this for coping reasons as well: you say to 'unwind' and mine was to 'forget'. It doesn't really matter what the reason is - as I don't think there is any reason to justify (or, to make it 'not matter') drinking that much alcohol in a week -- yes there are many many people who drink a lot more than that, but that is beside the point, too.
I could rant for a while so I'll to bee brief. You're correct in having a hunch that it may not be a good thing. If you didn't have ths idea, the question wouldn't have been posed. Also, you seem to be making it a point to hide this from others. You do it on weekends, and sometimes alone - you said your family and friends are not aware of the extent to which you drink. Why is this? Are you ashamed? Do you think you know what they'd say/how they'd react/what would be suggested, etc?
You need to find another way to unwind. Are you physically exhausted? If not, can you exercise? I'd try to exercise every weekend while tapering on your alcohol intake. It's best to deal with this potential problem NOW while you're young and at this point (rather than 2 'bottles' a day) than later on when it's clear to everyone you have a problem, and you're too messed up to realize it (and worse, to deal with it and get well). If you need a little help, maybe you could see a psychologist - is this an option for you? I'm not saying you need medication (psychiatrist) but rather some cognitive therapy to deal with the root issues while tapering, or to have someone else to work out a tapering plan or plan of action with.
Exercise works wonders (in SO many ways), make sure to eat well so your body can function and your mind is (in turn) 'fresh', get 7 hours of sleep (more/less), and make sure to not be a hermit! I know that if you're working or taking courses (whatever it may be) during the week, you can become exhausted by the time Friday rolls around, but make sure you don't become too isolated. It's important to have people you can talk to, or even just be around, if need be. Check out this text for some (LOTS of) information:
http://books.google.com/books?id=2OJV12astRUC&lpg=PA19&dq=consequences%20of%20alcohol%20when%20young&pg=PA22#v=onepage&q=consequences%20of%20alcohol%20when%20young&f=false