You're not alone! I did the same thing - left 3FC, and gained everything I had lost back +10
But all that matters is that you stand back up one more time than you fall. And you're pulling yourself back up now.
As for how many calories? The basic rule is more calories out than calories in
Here is a calculator
to determine how many calories you burn in a normal day based on your age, gender, height, weight, and activity level (ie, I burn more calories on a daily basis because my job is running after 2 year olds as opposed to a desk job) In order to stay your weight you'd want to eat that many calories. To lose weight, stay under it.
IE; Mine tells me 2727 calories per day. I try to eat 2000 or less calories per day (meaning I'm staying under 727 calories a day) plus workout.
Remember, a deficit of 3500 cals and you'll lose 1 lb. It's a good idea to try and stay around 2lbs (so 7000 cals) per week, but more or less depending on how much you weigh.
As for personal tips I've picked up;
1, Measure yourself! You'll find yourself not believing the numbers, or you'll feel like you're not losing fast enough with gaining muscle. If you measure from the start and re-measure again later you will have proof of what you've really lost!
2, Exercise! The last time I tried this I just changed my eating habits and didn't really exercise - but this time I'm working out every day - The weight is coming off faster, and I have extra energy.
3, Do not do not do not deprive yourself. When you tell yourself "I can't ever have this again" you will feel less motivated, and be more likely to binge and then give up. Find low cal/fat versions of your favorite foods. (ie, weight watchers or skinny cow deserts, or go to Hungry Girl
for healthier versions of unhealthy food, or just plain out allow yourself a small amount of your favorite unhealthy food every so often as a reward - just don't overdo it!)
4, Water! Lots of it! You can buy those crystal light packets to add to your water to make it a little more flavorful if it makes it easier for you. Just be prepared for lots of trips to the potty. (I didn't nickname myself pee girl for nothing!)
5, We're all human - we're going to slip up and have binges or lazy days. But just remember to pull yourself back up and get back into your new healthy habits!
and 6, Exercise! Oh, I already said that? I'm just feeling so much better even after just a couple days of working out that I can't say it enough!
Good luck, and know that everyone at 3FC is always here to offer you their advice