Women think far too little of themselves, and give too much of themselves away.
The best thing that you can do - is get yourself into his position , and date three or four guys at the same time - so you can see what it is like.
When I was younger I saw a guy who was dating lots of girls and he hurt me. Women are often told by men, that we are only allowed to be with one man at a time, while they are happily seeing many women. This is not true! Grab your power back.
I wised up as I got older, and I always date more than one man at a time bow.
Right now, I am dating four men. None of them know about each other, but none of them think that we are exclusive either. They don't ask and I don't say.
Now I am in this position, I can see exactly how the men feel like when they do it.
Why would I give any of the four men up? I get four lots of men, I get four lots of attention, four lots of romance, four lots of loving texts etc. I get loads of good things.
He is not going to give those women up.
Get your power back and date more guys than just him!