When you said it was a disaster, I was thinking someone was rude to you or you tripped and fell on your face or something. One pound isn't a disaster! My weight can fluctuate up to 5 pounds from day to day, and I'm fairly short/small. So a one pound gain doesn't even phase me anymore... I look at the trend over time. I do weigh once a week, sometimes twice, but I worry more about what I weigh now versus a month ago.
If you've been following your WW guidelines pretty closely, there's no way you gained a pound of fat in a week. You'd have to eat 500 calories more than your
maintenance calories every day... which is probably more like 1000 more than what you are eating on WW.
You wouldn't gain a whole pound of muscle in a week (I wish that were possible!) but sometimes when you work your muscles harder than usual they hold on to more water.
It's probably extra water that you're retaining for some reason. Did you eat anything particularly salty the day before (packaged soups/dinners, restaurant food, salted chips/pretzels/crackers)? Have you been sure to drink lots of water -- even more than usual now that you're exercising more? Some women gain water weight at certain points in their cycle. Some people get bloated if the weather is warmer than usual.
Did you wear more clothing than last time? Are you feeling as *regular* as usual? Did you eat anything before?
Lastly... sometimes your weight will do funny things, good or bad, that you can't explain. Don't let it throw you off plan... just keep doing what you know you should. Even when the scale isn't dropping, you're getting healthier and stronger and that's always worth the effort!
Edited to add: sorry for writing you a novel here, lol... I haven't had much time for the forums for the past few weeks, and I'm just happy to be posting again.