Swelling left neck face and leg. Negative for blood clots. Drs can't find anything. What could be causing this. Had CT and ultrasound. All neg.

Multiple issues. Could be a medication side effect, could be an enzyme deficiency if you have people in the family swelling too, c1 esterase inhibitor level and function and c1q need to be checked among others. Consult an allergist if you are at your wits ends.
Is this something. Easily visible to others or do they have to look very closely? Are you in pain? Are u still able to move ok? The face and leg would be unrelated, i can't think of a process that would cause swelling in both. One sided leg swelling in absense of clot can be hard to solve. Have u lost weight? Sometimes that can result in uneven size in legs. Doesn't sound like bells palsey, r u sleeping at night?