login to site and password

Hi – every time I log into my website, I use the password I created the last time I logged in. Because every time I log in it does not recognize the password and I have to request a new one. Does anyone know if there is a way I can fix this? I wondered if it is because I’m using the same email address as my username on several training courses I’m enrolled in and they use wordpress as their sites. Help!! I don’t want to have to put in a new password every time I log into my site.

Thanks for your help in advance!!

Sonja