There are many reasons you could have "gained" 6lbs in a week, and most of them are temporary.
If you have eaten lots of salt/sodium this week, or changed your fitness routine, it could just be water retention.
You could be about to start your period- Especially since you said you skipped it last month. Hormones can wreak havoc with your weight.
Make sure you are drinking plenty of water and eating plenty of good for you foods, like fruits, veggies, lean proteins, etc. The weight will likely go down soon.
Don't let your weight get you down. Do you have other markers for your healthy lifestyle? For example, do you do measurements? Have you had your body fat percentage measured? Do your clothes fit better than they did? Do you exercise at a high intensity level than 3 months ago?
Weight is only marker for success when it comes to healthy living, and it really isn't the best one, either.
Keep calm and exercise on!
Edited by: WHOLENEWME79 at: 3/14/2013 (13:30)