What kind of blood test did my gynecologist perform for pregnancy?

Probably bHCG test. Usually the chemical tetrs you get from your doctor, and do at home are designed to detect bhcg, or beta human chorionic gonadotropin. These tests can be inaccurate if done too soon, with some false negatives, as it can't be detected until implantation. The rosette inhibition assay for early pregnancy factor (epf) can be done 48 hours after fertilization, but is costly and long. U/s also done.