My boyfriend wants me to be bisexual???

Hey girls I have a question,

So i have been dating with my bf for 1 year and nowadays he is acting weird. I am straight as far as I know and I don’t have anything against lesbian, gay, bisexual etc. He keeps saying that it is okay if I have sex with a girl many times and I really don’t feel like I want to try that while I am dating with someone. It makes me sad knowing that he is okay with me having sex with another girl. Why do you think he is acting that way??

Thank you all for your answers!!!