I have an exercise addiction. if i exercise less will i gain a lot of weight?

Not necessarily: If you start exercising less it means that you have to be more careful about how many calories you eat. Less physical activity means less calories burned, so you have to eat less to keep your weight stable. Best of luck.

Not enough data: The answer is likely no, but without knowing your daily caloric intake and energy expenditure, it is impossible to say. Generally, reducing your exercise level will not cause weight gain as long as you reduce your calories by a similar amount. Recommend seeking treatment for this addiction with a qualified professional.