Well I mean all ESTPs aren't the same. Sure, an ESTP could employ Se/Fe to manipulate to get what he wants. I have felt sometimes like my xSTP (let's just call him STP for now) is too reserved to be ESTP but too Fe at times to be ISTP. His own mother says he's manipulative, and sometimes I feel like he's being pretty selfish, but then he recants later and shows that he's not selfish, you know? Like he acts selfish but then will turn around be a good boy to make up for it a day or a week or two weeks later (whatever), or do exactly what was requested of him, even though he wouldn't just the day before.
If you guys haven't been dating long, it probably is still infatuation and you should act accordingly. If you follow the Artisan/SP temperament (for ANY SP) they're going to be mildly suspicious of you and act in their own best interest in the beginning because, as Keirsey says, realize all humans have "feet of clay." I think STPs are more inclined in this direction than SFPs, to a more serious level, while occasionally an SFP will just naively take you in because they Fi immediately like you, but then will drop you just as quickly IF YOU CROSS THEM.
Going by functional order, refer again to the possibility of Se/Fe manipulating others to achieve self-interest. ESTPs are supposed to be excellent sales people. We've had quite a few ESTP presidents here in the U.S. Famous ones too, like JFK.
Anyway, yeah, all ESTPs aren't the same, and what you perceive as "selfish" could just him being guarded and cynical, or actually just being clueless about other people's feelings, as young xxTPs often are. Being clueless about other people's feelings doesn't necessarily equal malicious intent or "bad person."
Give it time, but if you have this sense of him being selfish, remember to self-preserve and don't just give him everything, yet, until he behaves in a more concretely loyal manner.
