Tomato plants need to be pollinated, so sometimes just gently shaking the plant helps. It's an old trick used by hothouse growers. You are better off giving your plant deep drinks of water whenever the soil feels dry 1 to 1 1/2 inches below the surface, rather thank giving it daily drinks. The yellow blossoms will seem to disappear, but you should see little tomatoes developing in place of the previous blossoms.