Why am I not losing weight on Weight Watchers?!?

I have been on weight watchers now going through the middle of my 3rd week. The first week I lost 3.6 lbs..2nd week I gained 2 ounces...this week I've weighed myself and nothing still the same???? I've been excercising walking and hiking 3 to 4 times a week. I've been writing my daily intake and have been within my points. Though I have noticed I've been eating dinner late due to excercising and getting back home late...I'm not sure if this might be causing the problem...but I am getting a little discouraged not seeing results especially in 3 weeks. Please motivate me!