Nothing to add, just want to say I agree with the advice already given:
1) Don't compare what he's done for others with what's going on in your relationship now. It makes it sound as if you're keeping score (when does he know whether he's "won"?)
2) He definitely does not need to be in constant contact with his ex -- especially not when the two of you are out together. (Just out of curiosity, do you know if he's a textaholic in general -- one of those people who would need major surgery to separate them from their electronic gadgetry? Or does he only ever seem to be texting his ex?) Dips had great advice there; smile, say you'll see him when he's not so busy, and leave. That will give you a barometer reading as to what is going on and whether this relationship is worth working on. Hopefully he'll smarten up -- but if not, better to find out now than before you invest a lot of time and effort.