10,000 steps a day DOES work if you're currently not doing any exercise. For most people, 10,000 steps a day is almost 5 miles.
With any proper nutrition plan, exercise plan, modification, whatever, you are always going to have plateaus. It is part of your body adjusting to the good, healthy changes you are making. Push through the plateaus and know that by eating right (weight watchers is wonderful) and adding exercise (10k steps is nice because it isn't overbearing or difficult), you are doing things that are healthful and helpful to the body.
I know it can be discouraging to be working so hard and not see any numerical results on the scale but also try to look for improvement in other areas. Personally, I've been stuck for weeks at a weight that is 13 pounds from my goal, but in the meantime I am seeing muscular definition in my body and fitting into clothing sizes I haven't worn in ages! So, even though the weight isn't coming off my body is changing and responding to the good things I am doing to it.
Something you might wish to try. I am going to guess that with WW you have either a range of points or calories to eat each day or for the week. I am not sure how you divide up your allotted points, but try doing a 'bounce between'. In other words (just for easy numbers' sakes) let's say you have 70 points a week. Instead of eating 10 points a day, try doing 8 one day, 12 the next, 9 one day, 11 the next and so on. Sometimes people plateau because the body's metabolism gets into a 'rut' so to speak, and by bouncing up your calories a bit you keep the metabolism on it's toes. NEVER dip under the number of calories per day you are supposed to consume because your body will start to go into starvation-survival mode. And, as you have probably learned at WW...you have to eat to lose weight :)
Congratulations on your efforts thus far and don't give up!