You are having an allergic reaction to the shell fish. The benadril may help, but if not, go to the hospital. This can become anaphylactic shock where your throat swells up where you cannot breath. This is what is called "a true emergency" because if the EMT is not at te Paramedic or Intermidiate level and can give drugs to counter act the reaction you go into shock.
look here
http://www.emedicinehealth.com/sever...article_em.htm