Welcome to the forum!
While I don't think everyone has the ability to "intimately" love more than one person, I certainly know some people can!
Polyamory is not all about sex but sex is the defining level of intimacy that separates it from other forms of love such as the multiple love for children analogy...for me the two types of love are completely different.
There are many approaches to how the word "polyamory" is used. Sometimes it is used as an easy way to screw around in my opinion, sometimes it's about friends with benefits, sometimes it's about a solid degree of love, and sometimes it's about life long relationships of "spousal" commitment.
I would be a little concerned about your boyfriend's history of feeling he is a "ladies man". I can't say for sure because I don't know his depth of relationship with his two girlfriends.
I think you need to ask each other and yourselves what it is that makes your relationship worth the work you need to do. Expectations, goals, long term ideas of what things will look like.
I definitely don't recommend you try something you do not actually desire for yourself. It is very normal to be attracted to other people. I'm not sure exactly how you go about trying to see if you can be polyamorous in the sense of loving more than one person. I figure you just fall in love and realize it then. You don't want to do anything that might possibly take away from your own sense of self worth. Do things because you want to. You are in control of the situation.
Take care and do what is right for you.