what’s wrong with me ?

so the boy that i am really close with and i have been doing “sexual things” and last night we were doing that and he was fingering me and it was really good and i was enjoying it but i just couldn’t finish and idk why because it was good. and now he feels theres something wrong with him and that i’m not that into him which is wrong cause i’m crazy about him and want a relationship but idk what to say to him now and why can’t i finish?