Trying, but really, why bother

Monday I rode my bike for 35 minutes, did some push ups, squats, sit ups, and stretches. Today was a 2 hour delay and I rode my bike for 20 minutes this morning and plan to ride again tonight. What I am upset about is that right after lunch today I weighed myself at school at 212 pounds. Then when I got home I measured my waist and it was back up to 43 inches. What is going on? Up, down, up, down My scales in the morning was 204 and after school I weighed 215 same day, same scales. Right now I feel bloated, fat, and discouraged. Why keep trying when I am not seeing results?