Before you break it off with him (and you may have to if he's being an attention whore), you should sit down and discuss this with him. Calmly.
I had something similar happen with my husband. There was a gal crushing on him. He wasn't interested in her, but he also couldn't not be nice to her. He found it embarrassing. Slightly different situation than yours, I think but the same solution might work for you.
Basically, he & I sat down together and worked out *together* how we wanted to handle it. First of all, I sympathized with him. Took his side in the matter. As opposed to attacking him about it, which you seem wont to do.
Then, when he knew that I understood this gal made him uncomfortable we deliberately did things to include her, but make her subtly uncomfortable. We asked her to go with us to things (e.g. the museum or dinner) but I would make sure I looked fabulous and we engaged in lots of PDA to the point it made her uncomfortable to be around us. Kill her with kindness, take the high road and most of all, be confident. It took a few weeks but eventually she got the hint that her crush was pretty hopeless. She even came to visit us once, LOL, but again we kept it light and friendly. I made sure I was there for dinner, etc and they were never alone together.
You should also ask him to limit his text responses to her. Not cut her off immediately, but suggest he answer far fewer and take longer to do it. When he does answer, the response should be 'business', not chatty.
If he can't agree with you on this, then you are out of luck and should move on to someone more mature. If he ends up with her, don't worry about it, you aren't losing much.
Good luck.
Last edited by IndiReloaded; 10-07-10 at 12:44 AM.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh