If you eat less calories in a day will you gain weight?

I lost 130 lbs 25 years ago and I just reduced my food intake to every 2or 3 days. i would just drink water on those days very seldom I would also have a sprite. My life since I lost the weight would be maybe 1 very light meatless meal a day and still only drink water. I walk 2.5 miles a day and go to the gym 2 times a week and work with some weights not real heavy but I have a 30 minute routine. I have gained 25 lbs in 8 months. I don't know what to do. i feel like I'm gaining weight daily. i'm 62 years old and work full time, I'm very active. I have a 13 yo son, so I'm also running taking him to his events. can someone help me. If i eat I will gain but I'm gaining ny way. I'm so depressed.