My super-attractive and successful boyfriend and I have been together 6 months. We’re long distance, and I’ve been so afraid of him losing interest, that I’ve put a great deal of work into initiating contact, (every other day I text him first – flirty messages or sincere appreciation for something he has helped me with) asking him for a shirt of his to wear to bed, complimenting him, etc. We’re both older (42 and 34), and he’s always telling me how great I am, but that I do not give myself enough credit. He has been chatting with other women lately – I found him on the site where we met because my counselor told me he shows signs of a cheating guy, and suggested I look online. I confronted him, and he said he is talking to 3 girls in 3 states but that he hasn’t met them. I suggested we have the option to see other people if we want- I think he’s doing it anyway, so he agreed.
He keeps hinting that he likes to “earn” someone’s affection, and that I need to EXPECT that he wants to stay with me, only have eyes for me, and that he will treat me well.
I finally see now what he’s saying. Basically, he’s saying that all the things he thinks are so great about me are diminished by my low self-confidence.
So… How can I be more challenging to him? How do I show him that I EXPECT him to come to see me, to call me? He never initiates coming to see me. He always says for me to let him know when I want to see him again and he will make it happen, which is very confusing to me…

You can be a challenge by NOT calling or texting him. Let him actually contact you. If you two were in a healthy relationship, both of you would want to contact each other. If you want to play games even further, go to the same chat area that he does with a username he recognizes. Start actively chatting with other men.
OR you can just end things and actually find a more suitable partner.
Truth is a guy is either attracted to a woman or not. You can’t do much to change it. He sounds like an asshole, you should find someone who actually puts in effort.
Honestly, I think you should examine yourself. You may have self-esteem issues that go beyond your relationship. For starters, when you told this man that you were okay with both of you seeing other people, were you actually okay with it? Or were you just suggesting it because you thought he’d do it anyway? And now, trying to change your behavior…is it because you want to feel better about yourself and your relationship, or because you have a need to please?
I’m not saying that this is a bad relationship. Obviously, if he tells you that you don’t give yourself enough credit, then he cares for you greatly. I’m just saying that you need to work on your self-esteem and discuss openly any issues you may have with your self-esteem or with the relationship in general.