Who can help me with bodybuilding?

hey evryone im 5’7 last time I check that was quite awhile ago so iunno now I weigh well im not sure but I weighed 180lbs just about 2 weeks ago and scince then I feel very week and I cheked the scale and its an electric one and it said 169lbs and I kept doing it over and over what happened this was like a month or 2 ago and I havent been working out scince then just pumpin dumb bells when it happened I wasnt working out as much eather I was staying at my g mas during the time and she feeds me very little like the size of a dessert plate so that cut my eating down and I ran to school evry morning whitch is like a half mile away then from 9:30-11:45 I would jog at night and in the day time from 4:00-6:00 I would do parkour and I only ate supper and the odd time a bowl of cerel for breakfast what happened I want to spend no money and get buff now im not fat just built like a birck house what happened?