yes it is possible. Usually when you have been treated with anti-biotics they will test you again to ensure that it was entirely cleared up. Were you tested again right after you finished your course of anti-biotics?
It's really hard to give a definitive answer. Having sex with a condom often prevents transmission, it could also depend on how many times you had intercourse, the more times you did it the greater the chance for him to contract it. Although it could be due to the fact that it is easier for women to contract STI's from men than it is for men to contract STI's from women.