You sound really sad & scared, which is good because you know how bad bulimia can be for you! I was bulimic for 10 years & I was afraid to tell anyone ~ but believe me, that is no way to live.
The best exercise for me is walking. Whenever I got the urge to binge, I would put on my headphones & jus take a walk wherever I was, either outside or on a treadmill at the gym or in a mall on cold or rainy days. It's nice if you have a friend or relative to walk & talk with, too. Try for 1/2 hour every day, then eventually work up to longer walks.
With all that exercise, you need to eat ~ but real food. I found I had to totally give up all of my bulimic trigger foods ~ white flour, sweets, ice cream, fries & fast food. At first it was hard but I replaced them with healthy fruits, veggies, whole grain breads, nuts, & yogurt. You can eat alot of that kind of food without gaining weight. I make sure to eat regular times, breakfast, lunch & dinner every day. Whenever I skip a meal or don't eat enough (not binging, but feeling comfortably full) I start getting those old binge urges again.
You can stop purging & start living. Your body is messed up, but it can heal itself. Have patience & be good to yourself. You are dealing with a deadly disease & you are doing the best you can to get over it. You can do it!!!!