wordpress losing session on page refresh

Hello, I’m trying to develop a plugin for the wordpress and i’m having a small issue with the session. I have created my own login page for my plugin and when user puts his username/password and sending an ajax request to check if user details are correct or not. The function that the ajax is calling is stored inside my index.php of my plugin. Using the $_SESSION in the function that ajax is calling, i can print the variable that I want, but then if the data are correct the ajax reloads the page. When the page is been reloaded the session no more exist. Does anyone knows how i can solve this problem?

Thank you