Not loosing weight inspite of excercising and eating right?

have been working out in the gym for last one year. i am 41 years of age with 2 kids. Initially i lost about 4 kgs now i seem to be puuting on weight inspite of regular workouts and eating right. What could go wrong? i am very demotivated as i am trying so hard to loose weight. can anyone suggest .my excercise regime comprises of 30 to 40 minutes of cardio and another 45 minutes of various excersies. i use mild weights as well and work out on abs thrice a week with minimum 250 crunches. can anyone help.