1) It tastes watery because it's not carbed.
The co2 of carbonation goes a long way to lifting flavors and aromas to our tongue and nose. It appears thin and watery because the co2 isn't there to give it the appearance of more body.
You ever pull a soda at a fast food joint that the gas wasn't working? It tastes watery too. The mix is exactly the same whether it's flat or not, but that carbonation is what gives it a fuller mouth feel.
2) It's not carbed because it's only been a week AND you're storing your beer too cold for the yeast to carb your beer.
The 3 weeks at 70 degrees
, that we recommend is the minimum
time it takes for average gravity beers to carbonate and condition. Higher grav beers take longer.
Stouts and porters have taken me between 6 and 8 weeks to carb up..I have a 1.090 Belgian strong that took three months to carb up.
And just because a beer is carbed doesn't mean it still doesn't taste like a$$ and need more time for the off flavors to condition out. You have green beer.
Temp and gravity are the two factors that contribute to the time it takes to carb beer. But if a beer's not ready yet, or seems low carbed, and you added the right amount of sugar to it, then it's not stalled, it's just not time yet.
Everything you need to know about carbing and conditioning, can be found here Of Patience and Bottle Conditioning.
With emphasis on the word, "patience."
3) Going by your airlock and when it starts or stops is a disaster waiting to happen. You really need to use a hydrometer to determine when a beer is finished fermenting. Taking 2 consecutive hydrometer readings over a 3 day period is the ONLY accurate way to tell if a beer is done fermenting.
And a week is even too soon to check. This is not making coolaid, time is your friend. The yeast are the only ones to tell you when they are finished with the job, and they have their own agenda. They can't read recipes and don't know a calendar for ****. So you have to wait and let them tell you when they are finished.
Many of us leave our beers alone for a month in primary, skipping secondary. But if you do choose to secondary, wait til you determine that fermentation is complete.
I suggest that folks don't even take their first of the 2 hydrometer readings til the 12th day, then again at 14 and if the gravity is the same you can rack to secondary.
I really suggest that folks whether or not they secondary or opt for a long primary, that they don't bother for one month. It gives plenty of time to ensure that fermentation is complete, that they yeast have an opportunity to go back after they are done fermenting and clean up after themselves all the byproducts they created during fermentation that leads to off flavors, and that their beer has a chance to clear.
Then you again have to wait the minimum 3 weeks, if not more for carbonation and bottle conditioning to occur.
All fermentations, including the carbonation process has the potential to produce byproducts of fermentation, the yeast is tossing off waste products as it goes along eating the sugar to ferment the beer or carb it. But when left alone, the yeast will usually go back and clean up those byproducts. That's why we talk about prolonging yeast contact and bottle conditioning.
The yeast are fastidious creatures and like to clean up any messes.
I would just pull the beers you have out of the cool place they are in, give them a shake, and leave them for a few more weeks, just to see if the yeast will make them better. I've found beers that were 6 months or more in the back of closets, that were pretty mediocre initially or downright crappy, that have been vastly better, with some extra time.
Your beer will be fine...and your future beers will be better, if you wait things out....