How can I discover who has been accessing my email account without authorisation?

For the past month I have had trouble logging into both my yahoo and hotmail accounts. On each occasion my pword was rejected and I had to follow the pword reset process. I suspected someone was accessing my emails (a bitter ex being the suspect). so decided to set up a trap. I believe that this person was attempting to access my hotmail account by following the pword reset process. This sent a pword confirmation email to my yahoo account. They would then access my yahoo account by knowing the answer to my secret question and resetting my pword. Once in my yahoo account they would then open the pword confirmation email sent from hotmail and reset my password to gain access to my hotmail account. To discover if my suspiscions were correct I directed any password resets to be sent to my work email. Low and behold I received an email last week asking if I wanted to reset my hotmail password. (I hadn't requested this). How can I catch catch this culprit?