Speaking of you having multiple people that you’re dating, it’s possible that the man you’re dating will be dating others as well. You didn’t already delete your dating profile, did you? Put it back up and in the future, deactivate it only when you’ve agreed to be exclusive with someone.
Back to the subject at hand: First, do not freak out. Honestly this is not a freak out situation. It’s not even worth swerving, sweating, or swearing over. Put on your big girl panties because this isn’t going to be the most comfortable position you’ve ever been in but you can get through it and even be improved by it.
How did you find out? Did he tell you? Kudos to him. Did you find out on your own? Not a good sign. Be calm and rational. Take your emotions out of it. Be willing to have an adult conversation where you discuss dating other people and where the line is. Can you come to an understanding? Are you willing to ask him to let you go if he’s approaching that line with someone else? Know where you stand so that you don’t get confused later.
Don’t drive yourself crazy thinking about the other women. Never ask him about them. You are not “winning” anything. Stop checking his dating profile. Concentrate on analyzing him for his suitability for you, not your suitability for him. If it’s a good match, it’s going to work out. If it’s a bad match, he will meander away from you.
Focus on being the best version of yourself possible and the competition disappears.