Hello, I Am Wondering I Have Been Treated With A

Hello, I am wondering I have been treated with a yeast infection twice already over the last three months and it seems to have cleared up over a few days using canastan. My boyfriend was also itchy and irritated and used the canastan cream for a couple days to clear up his itchiness. It seems everytime we have sex it causes me to have yet another yeast infection and him to have the same symptoms with the itchiness and irritation. Did he not use the cream for a long enough time or is there something that I did wrong? Please help