Hi there ~
I understand your concern. It might be rare but it seems like you are having an unusual reaction to eating fish. If this does not go away with medications, i.e. anti allergy
medications you might have to give up eating fish, if that is not asking for too much. I also think that it might be a good idea to consult an alternative medicine specialist like ayurveda doctor. I hope this helps.
Take care and have a lovely day!