Does a heavy period (on time) mean that plan b has worked? i am also on birth control (for over two years). should i be worried at all

Plan B: If you are already on birth control then you do not also need to take Plan B. The idea of birth control is to prevent pregnancy so taking Plan B is not necessary. If you were not taking them correctly then perhaps that is why it was added. In general a normal period means that you are not pregnant. You can always take a home test if you are concerned.