I took a plan b yesterday and i put it in, the cap of the lid of my drink and it started to dissolve would it still work ?

Yes: Plan B contains high concentrations of two hormones that interfere with the implantation of a fertilized egg. As long as you swallowed the whole pill (dissolved or not) the hormones were able to get into your system. Remember that Plan B is a backup. You should be using some other form of birth control regularly. High levels of hormones taken frequently can cause many side effects.