Bactrim one dose in help needed

prescribed bactrim for uti took one of a 3 day course 8 hours ago. woke up with hives and mild swelling on ankles and feet, swollen eye, swollen face, skin tightness on scalp, head pressure, facial redness. stopped taking the bactrim and took two Benadryl. waiting on prescribing doctor to reply, but worried bc I don’t want this to be a severe allergic reaction.