My (F 20) partner (M 21) of almost five years has recently told me he feels a need to explore his sexuality (through having sexual experiences with others) in order to better understand who he is as a person. I have been so supportive of him, I love him and want him to be happy. However, I can’t help but feel heartbroken. We are both in college, and live about an hour and a half apart, but our relationship is beautiful. We are best friends. He said that we would either break up, or open the relationship for him - which he knows would be difficult for me. I am a monogamous individual myself and our relationship has always been monogamous. I am considering it because I love him and don’t want to lose him or “give up”. However, I know deep down it would break me, make me insecure, and drive me insane. Additionally, we only see each other one to two times a month, and he has admitted that he puts more effort into his friendships at college rather than our relationship - that essentially he prioritizes his friends over me. He also recently told me he is attracted to his new female best friend. This is such a hard decision for me to make and I am heartbroken. I have always imagined a future with him and I am lost. He said if we separated perhaps we can find our way back to each other again. What would you do? Any advice would be appreciated.

TLDR; My (F20) partner (M21) of five years wants to open the relationship and I am torn and devastated