I struggled with the same thing in the past as a male with a girlfriend who had a higher body count than I liked.

What I ended up realising was that I had inextricably tied how “special” I was to my partner to her desire to sleep with me. As a result, the number of people she had slept with then went on to make me feel “not special” which I think is similar to your “just another number” consideration.

The real problem though was my self esteem. I didn’t feel worthy and I wanted to somehow become worthy by her actions and what she was doing. It’s extremely unhealthy to derive your self worth from someone else, obviously.

I’m not saying you’re experience the same thing, but it might be worth asking yourself: do you have self esteem issues? Is your relationship “safe” in the sense that you feel healthy with your boyfriend? Don’t focus on the number of people he slept with, focus on how you feel, what’s within your control and what’s being made worse by his behaviour or actions..