My boyfriend (M24) and I (F25) keep having conversations in regards to opening up our relationship. However, I have no desire to open my side of the relationship, this is partly due to myself having no wish to pursue any other relationship/hookups as I have in the past.

He [my boyfriend] has no other experiences prior to our relationship (sexual, emotionally, romantically, what have you) and wants to explore more sexual experiences, particularly with men.
For better context on this- we met in university and started dating after moving in together (friends to roommates to romantic relationship trope, I guess) and have built a life together been together for two years now.
We both see a future with each other and pursuing life together to it's fullest extent (marriage, kids) and want to keep our relationship healthy- which he sees as this a particular part of it [in terms of keeping it healthy ] and I do too, as it will make him happy to get those feelings out and I don't want our relationship to end because of it.

He has no intent on hurting me or not abiding by our rules and I don't wish to do the same as we both love each other very much- if I want it [the open relationship] to end, at any point he'd be willing to stop.
We've talked about rules and guidelines to make myself comfortable with the situation- in short form those rules include; safe sex/protection, no emotional ties [he has no desire to be in another relationship with any other partner], no neglecting our relationship, not in my space(s), no friends, communication/trust, etc. and keeping it straight-up hookups only.

I don't know what else I can do to make myself more comfortable and open to the situation, any advice and experiences would be appreciated.