Daphne --
I know what it's like to lose the weight and then, in an instant it seems, gain a lot back! I think we've all been there!
First though, you probably didn't gain 7 pounds of fat in three days. Go back on plan (sensibly) wait a few days and weigh again. Then you'll probably see the real damage (a few pounds).
Second, use it as a learning experience. When did it go wrong? What can you do better? I've learned
a lot from such situations. I know that if I am at a party and have "just one" of something that I like that I will crave more. And likely eat it. But if I resist, keep a drink in my hand, keep away from the food and talk to people that I am much more likely to be successful. I don't go to parties hungry but have a healthy snack first (less likely to be tempted...) Etc.
This is a lifestyle, and fortunately, we get lots of practice!!
Good luck!