i can’t cum!!

so i was a little bit of a late bloomer when coming into my sexuality and so for the past year i lost my virginity and started using a vibrator. i can cum while using the vibrator, but i can’t cum for myself without it or during sex. i always feel like i’m getting right up to that moment where everything feels so intense and i want it to keep going and i wanna go over the edge, but part of me also hates all the feeling i get and how intense it is. i can never cum :( any advice? or tips on why i feel so overwhelmed when i get to that point?