When you first start working out, your muscles get little tears in them. They retain water to help repair themselves. This causes a temporary gain on the scale. Keep working out! Also, remember that the scale is only one way to measure weight loss success. My friend didn't lose weight for 6 months, but went down 4 or 5 clothing sizes. Just keep at it and have patience! You are doing great! (Taking measurements to see how many inches you lose once a month is a great motivator).