If allergic to bactrim (sulfamethoxazole and trimethoprim) & ceclor, is allergy to all sulfa drugs & cephalosporins assumed?

Only if true allergy: Often, a side effect to a particular drug may by mistaken as an allergic reaction to a drug. If what you have experienced is a true allergic reaction, then you should avoid these types of drugs.

Depends: Ceclor is in the cephalosporin group and members in this group do not cross-react that much. If the reaction was an anaphylactic, consult an allergist before trying another cephalosporin. This is different from sulfa which you must avoid . On the other hand, recent studies have shown that sulfa allergy does not preclude you from using drugs with a so-called "sulfa-structure"