Advice wanted

I (cis F bi 44) have been with my boyfriend (cis M straight 46) for a little over 2 years. He is experienced in poly, I am not. We consider each other primary partners but the number of other partners he sees regularly has grown since we started dating. At first he had 2 other partners that he saw once every week or two, and some random hook ups, maybe one or two a month. Last month he has sex with 14 different women, some of them more than once. He often doesn’t even remember that he was with them unless I remind him. For him, having sex with as many people as possible makes him really happy, especially new people. I know he loves me but I don’t feel good about how many other women he is with all the time, and it’s hard for me to feel important in his life when we don’t live together, aren’t married, and probably never will be. I’ve been trying to figure out my boundaries without putting rules on his behavior.. but is it ok not to be okay with your ‘primary’ partner having sex with so many other people all the time? For me, I am mostly really happy just being with him,and having some sexual adventures together with him and others but I don’t have much of a desire to date a lot of other people.

I don’t want to put rules on him that make him unhappy, but is it reasonable to have a primary partner behave like this? Is there any way I can feel good (safe & happy) in this relationship when there is no outward sign of our commitment to each other (living together, marriage) and he is constantly with so many other people ?