Could my metabolism have adjusted to the amount of time i spend exercising ? my body just expects an hour of cardio every day. i gain weight if i do

Yes : As we get older our metabolisms tend to slow down and women have a noticeable change due to menopause. Most people tend to lose muscle mass which has negative effect on calories burned. Doing the same cardiovascular exercise will eventually pose less of a challenge to your body and give less effect. Adding variety, including intervals and strength training will increase effectiveness of workout.