My (28f) bf of 5 months (33m) just told me he's had sex with and feelings for his current best friend. What do I do?

How do i (28f) deal with finding out my boyfriend (33m) hashad sex with and has had feelings for his current best friend

My boyfriend of 6 months recently mentioned that he had sex with his female best friend shortly before we met. Normally, I wouldn't be bothered by a partner's past at all,, but this is different because of our history.

We originally started dating a year and a half ago, and things were going well until he suddenly ended things to pursue a romantic connection with another completely different friend. It didn't last long as it was obvious she confessed to him out of jealousy of me. They had been friends for 10 years and he had been single two years before he had started seeing me. She literally had two years to confess her feelings for him. She wasn't a good person, and he deeply regretted it almost instantly.

They broke up. Him and I were just friends for a few months before he admitted to regretting everything and we got back together.

That experience hurt me deeply, and it's hard not to feel a bit uneasy now knowing he has a history of exploring feelings with close friends. However, at the time when I decide to take him back, it appeared to be a benign mistake and up until now when he told me he has liked and slept with ANOTHER one of his friends before we met, I'm worried that maybe this is a potential pattern. He has many and I mean MANY female friends, and I NEVER worried about them until now. I assumed all those relationships were platonic.

I don’t want to be controlling or tell him who he can be friends with, but because this has happened before, I feel a bit insecure. I’d like to talk about healthy boundaries with his friends and hear some reassurance that I won’t lose him to a friend again.

How do I tell him in a non confrontational manner that this leaves me feeling a bit uneasy because of the previous pattern and that maybe we should discuss proper boundaries with his friends? Honestly, I might even just want some reassurance and for him to say "I'm not leaving you again for a friend again."